Dry preservative [ Borax ] will work great for squirrels too. I feel the skin on a squirrel is good and tuff for a first times taxidermist. Fleshing is better because of the tuffness of the skin.
Squirrels are pretty easy specimens to get compared to turkeys, geese and pheasants.You can easily bag several in a fewdays hunting. That way you have a few to practice skinning. You have to skin them when you clean them anyway.
I found skinning a pheasant a little more difficult than a squirrrel. I especially had trouble in the wing area. Ripped a few holes there. The rump area will also give a beginner some trouble because of the thin skin.
I'm in no way a professional taxidermist but I am an amature. I am just trying to give my opinion of which I thought would be easiest to start with based on my experience. I don't want to step on any toes here.
As for carding the ears on a squirrel, Ileave the cartilige in, thenI use "Lee Press On Nails". Just put one on the inside and a slightly larger one on the outside and hold them in place with a paper clip until dry. I almost forgot, remove the sticky stuff inside of the nails first.