So I got tired of all the Fox squirrels that get killed on my road and the two adjacent roads. What a waste. So this year I decided to skin them and learn to soft tan. So far I've picked up and skinned 15 since mid Dec all within 1/2 mile of my place. Only one that was too mangled to use, but 15 good ones. It's all wooded so I've seen maybe one or two fleas is all. People going to work and coming home fly too fast down these roads (30 posted) and hit the squirrels. It's like this every year. I put the carcases back out near where I found them but well enough off the road and they get taken overnight. I started off with a sharp utility knife, but a friend loaned me a Havalon Piranta skinning knife and I quickly got my own. Blades only last about 1.5 squirrels. I've learned to open the hind fir and tail with the utility knife to save the skinning blade for working the tail off, and the rest of the skinning. I'm cast skinning but cutting at the wrist ankles. Most of the time the skull is crushed or damaged from teh car, but the fur is not damaged. I've gotten much better at skinning over the course of doing the 15. Soon I'm going to start the tanning process using MacKenzie relaxer/degreaser, then pickling in their picking solution while monitoring the PH, Neutralizing, and drying patially, then tanning oil and stretching. I learned from a good youtube video by Amy's taxidermy. Might have a couple more in the next few weeks. When would you want to stop? When would they start losing their winter coat? If like horses or cats, they already are....with the longer days.

It sounds like you have a sound plan. I always send my furs to a tannery, but squirrels should be an easy place to start with home tanning. I'd think as long as the fur looks good to you and since you're just starting out (aka practicing) you should go ahead and grab them.

Do one at a time and write down everything

That would probably take too long. I'm up to 18 now. 2 yesterday and 1 today.

When would you want to stop? When would they start losing their winter coat?

You'll know if their shedding alot when you brush them. All squirrels except red/pine squirrels have hair, not fur. So it's a little different than fur. As long as they're not shedding you'll be fine.
What are you going to use them for after they're tanned?

I know fly tiers use the tail hair could be a market

That's what those around me keep asking. I don't know. I'm using this to lean to soft tan. I can use one to make a cat toy. I bought some beavery fur cat toys from New England Naturals and the cats love playing with them.