I bagged a couple of Grey Squirrels that had been shot as pest control due to high numbers, tree damage and little natural predators. They were also causing havoc on some bird feeding areas, so I skinned them and saved two of the skins to practice tanning. The meet is good eating and I'll save them for a stew.
Theres a lot of conflicting information out there in the world, but the one constant is the fact that people casually say "flesh the hide removing the fat, flesh and membrane layer" I tried for the third time to wet scrape this membrane layer off the hide without tearing holes, and its jolly hard.
My advice would be to remove the obvious fat around the leg area of the skin and any flesh on a smooth round pole, then salt/dry the skin pinned to a wooden board . Then, when dry just scrape off the salty crust and peel the membrane off like sunburnt skin. You'll still need to scrape with a knife, but only gently and you will actually feel like you are making progress.
Then treat the skin side with a tanning solution. I used most of one egg (or use the animals brains and some egg) and a spot of warm water rubbed in by had with the board with the skin still mounted, on a flat surface. Allow the mixture to soak in, in a cool but not too cold a place.
A tip - dont soak the whole hide in a solution, giving the fur a full soaking overnight. Every time I do this on squirrels the fur slips and you end up with very thin rawhide. Its not the end of the world as you can continue to make buckskin, but its a lot of work for a small pouch worth of material. I heard the same applies to other small furry animal skins such as rabbit.
After around four hours of soak, start to stretch, and work the skin as it continues to dry in a warm place, until fully dry. You can stop now and then, but don't let it get stiff. You can abrade the surface with a stone or sandpaper to fluff up and clean the surface, but I didn't as the skin is so thin.
Then give the soft fur a good smoke over a fire but don't let it get too hot. This helps to maintain the softness should it get wet, and helps in preservation over time. Hand cream, or Neatsfoot oil can also be put on for the finishing touch.
Now I've cracked the technique, I'm hoping to get some bunny's to make some nice warm winter mits, and of course some more stew :)