Eventually you will learn to use your speedlight in Manual, just as you learned Manual with your camera. To my knowledge, all of us use Manual speedlight, and most of us set flash output at 1/8, 1/4, 1/2, or full power, depending on subject color and Working Distance. Experimenting with a tripod, varying only your manual speedlight output is the quickest way to learn approximate starting point for illumination.
In the field, I take one speedlight photo, immediately view image on my camera LCD screen, adjust speedlight, and repeat. It will become second nature to you.

Ooh-Rah, Brother. I was with VMFA 542 at DaNang from May 1966 to November 66 when they rotated up to Iwakuni for O&R so I got transferred to VMFA 323 at Chu-Lai until Jan 67 when I had enough time to rotate up to MCAS Iwakuni, Japan. It was in late Jan 67 that I went up on a test flight in BuNo. 151410. We had just had techs from MacDonald/Douglas install newer J79 GE 15 engines in our Bird. Less smoke & 500 lbs per engine more thrust. Hey, a win-win huh?
NOPE. Test flight went great. Our bird looked funny on the flight line with no drop tanks or hard point racks. She was clean. We went up to try and break rivets. Everything went OK until we came in at FL350 for a TACAN 1 approach. Approach Control cleared us to the 38 NM DME fix, 184 radial Iwakuni TACAN. Once there, we were cleared for the TACAN approach with a GCA hand off approach.

All was great until we passed over station at 350 and then BOTH J-79s flamed out!!!
I was flying back seat that day and I put out the RAT and called Approach Control to cancel instruments and declare an emergency. I requested a flame-out approach to runway 01 and it was approved. We went on a wide downwind trying for an air start but No-Go. We went too wide to make the runway so the Tower lit the sea drome lanes for us in the inland sea 1 mile east of the base that the sea planes used.

At 3,000 ft. I command ejected us and I went first from the RIO position but everything went wrong that could and I went through the rear canopy with a malfunctioning firing Martin-Baker Mk 5 seat. The canopy was not blown but torn loose by my seat. I broke my left collarbone in 2 places, broke 3 ribs, cracked 3 more, broke my nose, my left index finger and for good luck, smacked my left knee on the way out.

We hit the water on January 27 th 1967 and nearly froze our asses off.
Iwakuni is just about the same latitude as Chicago. It was just like landing in Lake Michigan in January!!!.

My collar bone never healed properly and so I was relieved from combat flying. I got sent back to the States and re-trained as an ATC officer. I was re-assigned to MCAS Iwakuni as the Control Tower OIC for MATCU-60 (Marine Air Traffic Control Unit-60) for almost 2 years. I had a short stint as an ATC officer at Phu-Bai in 1968. That's where I got my second purple heart when During an NVA rocket attack, I was blown through the air. I still carry 5 pieces of shrapnel adjacent to my spine as a reminder.
My first Purple heart was in 1966 in DaNang while in the head shaving for my pre-flight briefing. I got winged in the right calf and 3 days later it got infected. Our flight surgeon examined me and asked when I got shot. I told him it was during an early morning nuisance attack. I got my first purple heart for getting shot in the "crapper". How humiliating.

I would like to know if anyone owns a Canon and a Nikon. I have a t3i and a few lenses, Tamron 18-270, Canon 70-300, nifty-fifty and the 18-55 kit lens. I shoot in manual but sometimes put the ISO on automatic. My sister-in-law has a Nikon 3200 with a kit lens and shoots in nothing but automatic. Her pictures have such better clarity than mine to. I have to post process most to get to where hers are. So it's either my not knowing what the heck I'm doing or is the Nikon known for taking sharper pictures? I was thinking of buying a Nikon 7100 and having both. I realize the lenses won't be interchangeable. Any advice? This is not a " Canon vs Nikon question". Thank you.