I have been using cameras in subzero temps for 50 years. Not occasional use either, but all winter in places with long cold winters. In Barrow snow that falls in early October melts eight months later in early June! Every day in between requires proper technique to avoid condendation.

Two significant comments that contradict commonly stated advice:

1) Warming a camera slowly does NOT help and does waste your time.

2) Ziploc bags work but are not recommended.

The most effective and safest way to warm up a cold camera is to use a tall kitchen size plastic trash bag. While outside in cold air put the camera (and/or other equipment) into the trash bag, squeeze out all the air and give the top of the bag a twist or two. Take the bag inside and place it in a warm place with good air circulation. Warm air blowing directly on the bag works best!

That proceedure will warm the camera as fast as possible. The thin plastic with no air inside (air is insulation and slows the process) not only allows quick heat transfer but lets you do other things if needed.

If a memory card or battery needs to be removed it is easy and safe. With a Ziploc bag warm moist air will get into the bag if it is opened. With a trash bag an arm can be run down into the bag without letting in external air. Just do it in a place with calm air, not under a fan, and keep the open bag top well above the contents.

I have been doing Arctic "winter photography" to the extreme and full time for 50 years. It happens that I don't do much fully automatic but I am still very familiar with how it works. Hence a suggestion:

Ignore that advice as meaningless and not at all important! Winter and cold have no connection to auto vs manual anything. Whatever you are already comfortable with will work in the same way it always has.

What you do need to learn is:

1) How to deal with condensation when you take a cold camera into a warm environment.

2) How to keep spare batteries warm and available.

3) How to avoid breathing on a cold camera in a way that fogs it up and makes it useless.

There are lots of articles available via Google that will give you very accurate information on items 2 and 3. Searching for info on item 1 gets more BS than can be imagined!

Do NOT use Ziploc bags and do NOT think warming a camera is best done slowly!

Use a kitchen size plastic trash bag. While outside in the cold put the camera and lens(es) into the bag and squeeze out all of the air. Twist the top once or twice and take it inside. Place the bag in a warm place with good air circulation. The faster it gets warm the better.

The disadvantage of a Ziploc bag is that opening it in any way will allow moist air into the bag. With a plastic trash bag you can run your hand down into the bag to retrieve a memory card or battery and it will not let air into the bag. The top does not need to be sealed, it just needs to be above the contents and not have air blowing down into it.

As soon as the contents are warmer than perhaps 40F they can be removed from the bag.