1. IMO it really doesn't matter if the dust test image is focused or not.... But it does need to be a "plain, blank" image with no detail where specks of dust can "hide" (and sometimes that may be easier to accomplish with a de-focused lens). A patch of blue area sky will work, if you don't have anything else at hand. Note: If you use the sky and are using an auto exposure mode, the camera will want to underexpose so dial in +1 to +2 stops of Exposure Compensation. That will insure the image is bright enough to clearly see the dust on the sensor. Also be aware that a speck seen in - say - the upper, righthand corner of the image is actually located in the lower lefthand corner of the sensor when you view it from the front during cleaning (both firmware/imaging software and the camera's optical pentaprism "flop" the image to it's correct orientation and turn it right side up for viewing).
2. Flash might be helpful if you are working in a relatively dark space... rather than boost the ISO to shoot by available light, which will cause image "noise" where a speck of dust might hide. Just be sure that the flash illuminates the target evenly and isn't overpowering.... gives a reasonably "correct" exposure (a white target will want to underexpose, so once again +1 or +2 stops of Exposure Compensation might be needed).
3. There is risk cleaning the sensor yourself and to do it right you need to invest in some tools and supplies. But $70 for a sensor cleaning seems high. I've seen it done for $25 to $50. But maybe they do more than just a sensor cleaning. If not, shop around... Or learn to do it yourself. To minimize the risk you should read, fully understand and carefully follow the directions at
http://www.cleaningdigitalcameras.com/. The guys who wrote and maintain that site are professional repair techs who between them have probably done thousands of sensor cleanings. One of them (Larry) has literally "written the book" on camera repair. Well, actually he's written dozens. They also own and operate one of the largest suppliers of tools and supplies for the camera repair and service industry....
www.micro-tools.com. They sell virtually every product for sensor cleaning and are unbiased in their recommendations. (Unlike many sites that are promoting their own products and so are VERY biased.)
It will cost you more than $100 to acquire the tools and supplies for proper sensor cleaning. But once you have those and know how to use them, you'll be able to do cleanings whenever and wherever needed... plus the consumables will be enough to do multiple cleanings and are relatively low cost to replaced. Personally I use:
1. A Rocket Blower.
2. A lighted magnifying loupe.
3. Dry "adhesive" method cleaning kit (I use Dust Aid).
4. Speck Grabber.
5. Anti-static brush.
6. Pec pads for wet cleaning.
7. "Wand" tools for use with pec pads (two sizes: full frame and APS-C, to match the cameras I use).
8. Eclipse sensor cleaning fluid.
9. SensorPen (same as LensPen, but with a square pad instead of round)
10. A low power mini-vacuum (I think it was made for computer keyboards).
The Rocket Blower is used the most frequently and between other steps. It's a "no touch" device and I always try it first, in hopes of puffing away the dust. It's also useful once another method has loosened adhered particles. But it can't remove adhered particles or oil specks. The low-power mini-vacuum serves a similar purpose at home (while I always take a Rocket Blower with me).
A camera that's never had a sensor cleaning almost always needs a "wet" cleaning with the fluid and swabs. This is because there's nearly always some oil specks on the sensor (well, actually on the protective filter in front of the sensor). That oil was probably excess thrown off by the shutter or mirror mechanism. It's common with a new camera or even an older one that's never had a sensor cleaning. Oils can cause dust specks to adhere and dry cleaning methods won't remove oils, will merely smear them around. In fact, some of the tools used for dry cleaning would be contaminated and ruined by the oils.
For wet cleaning I make my own swabs using the "wands" wrapped with Pec Pads that have been cut down to size, and are held in place with small strips made from Avery labels. One of the key things with wet cleanings is to only use the swab twice.... once each for a pass in each direction. If that doesn't fully cleaning the sensor, then a fresh swab is needed. Another VERY important thing is to use minimal fluid... just a drop to moisten the swab. Too much fluid might seep behind the filter or elsewhere inside the camera. I only use or move on to dry cleaning methods when I'm sure there is no oil on the sensor.
The dry "adhesive" method uses another type of wand that's fitted with a slightly adhesive, single-use "pad" that's gently pressed on the sensor to "grab" dust particles. There are also "gummy", multi-use (cleanable) adhesive method tools. The Speck Grabber is sort of a fine, pointed version of those... used with the lighted loupe when there's just one or a few stubborn specks remaining.
The anti-static brush is similarly used to coax loose adhered particles.
Often sensor cleaning is a multi-step process, requiring two or more of the cleaning techniques and some additional test shots or close inspection with the loupe. I also use the bulb blower (or mini-vac) in between steps, to be sure any specks I've loosened and dislodged are removed from the camera.
The SensorPen is a final step and is used to gently "polish" the surface, especially if a wet cleaning was done because that usually leaves behind some slight haze. It's very important that any and all specks of dust be removed before using the SensorPen, because some dust can be hard particles capable of scratching the surface or the coatings on it. This final polishing not only insures as clean a surface as possible, it also makes the surface more resistant to dust adhering for a while in the future and can help camera's self-cleaning sensor tech work better.
Obviously, the swabs and fluid are consumables that will need to be replaced every so often (though there are many drops of fluid in a container and the pack of Pec Pads I bought is probably good for about 1000 sensor cleanings... except I also sometimes use them for lens cleaning, on my eyeglasses and for other things). The SensorPen, anti-static brush, Speck grabber and any multi-use dry/adhesive method all become contaminated over time and should be replaced occasionally, too.
>>>> WARNING >>>> NEVER, EVER use "canned air" to blow out dust in a camera. It is too strong a blast and might damage delicate mechanisms. It also can blow propellant liquid onto the sensor and even can super-cool things dangerously.
>>>> WARNING >>>> NEVER, EVER use common household "cotton swabs" ("Q-Tips", etc.) anywhere inside a camera. Those tend to shed tiny, tough fibers that can get into and jam fine mechanisms such as the shutter and mirror assembly. If that happens, repairs will be expensive!
Finally, I DO NOT clean the mirrors or focus screens in my cameras with anything more than a puff of air from the bulb blower. Those are delicate items that are all-too-easily damaged... The mirror is front-surfaced with vaporized aluminum... and many focus screens are optical plastic. But mostly, there's really no reason to risk it. Anything on the mirror or focus screen (and seen in the viewfinder), WILL NOT SHOW UP IN IMAGES. The mirror is lifted up and covers the focus screen during exposure (and during sensor cleanings). So I just tolerate anything on there (if blurry, it's on the mirror... if more sharply defined, it's on the focus screen) until I have the camera serviced by a professional tech every so often. Many cameras also have "light seals" around the perimeter of the mirror when it's lifted, which can be delicate and may need professional replacement periodically.
P.S. It's virtually impossible to keep a sensor perfectly free of dust. Don't fret about changing lenses because it really won't matter... Lenses suck air in and out of the camera whenever you zoom and/or focus them! But also use common sense during lens changes. Keep camera body and lens capped whenever a lens isn't on the camera. Occasionally clean the rear elements of your lenses, inside lens/body caps and even vacuum out your camera bag. Also, don't use ridiculously small apertures... only use as small as you really need. At larger apertures, the dust may not show up at all in images. Super small apertures cause diffraction, anyway... which robs your images of fine detail (smaller than f8 to f/11 on APS-C or smaller than f/11 to f/16 on full frame).
1. IMO it really doesn't matter if the dust test i... (