I use them for wings on streamers, wet flies and jigs and tails on nymphs like Ed Shenk's Big Gray Nymph. IMHO, squirrel tails look good with grizzly hackle collars. They are on the stiff/slow to sink side so better when fishing streamers/jigs fast and high. Softer materials have more action at slow speed and "collapse" and have less drag when pulled so they sink faster. The soft to stiff hierarchy used to be something like marabou - Arctic fox - bucktail - calftail - squirrel tail. Wing material adjusted to get the action needed. Marabou can move just sitting there in a stream - squirrel tail needs to be worked. Used to tie with squirrel tail a lot at one time and would go through tails. Material is a little slippery to tie in and the base hairs are softer.
The base of the squirrel tail has some meat in it so you need to do something to keep the meat from rotting. I used to let the end of the tail sit in salt (or borax) until completely dried. I did this more when I was young because I was broke and liked free materials and used more squirrel tail. (back in the day used a lot of pheasant tail, muskrat fur, deer hair etc because of free supply from hunters). Now I don't use it much so I buy squirrel tails when I need them every few years. Not that expensive and can pick from a bunch at a shop/show to find a good one. Also, the most expensive fur I ever got was free. DIY runs the risk of introducing pests or getting your materials to smell funky, so if a free material contaminates your good stuff it isn't worth it.
