The issues with the squirrel were varied. First, I kept having a lot of it pull out. I think that was due to using too large of a clump and not cutting the thread into the butt ends. Secondly, I was having a hard time keeping the squirrel on top of the hook shank. I found this technique which solved that problem. http://globalflyfisher.com/tiebetter/hardhair.htm
A drop of Dave's Flexament or thinned Sportsman's Goop (you thin it with toluene) put on the thread base just before tying in the squirrel (or for that matter any hair, including when you spin deer body hair) will do wonders to hold the hair and keep the number of thread wraps down to about 8-10. Easy to do and hold the hair with a vengeance.
I've found with squirrel or calf that if you wrap a thread base up to where you'll tie in the wing and then run super glue up the thread and use 1 soft gathering wrap and 3-4 very tight wraps, the squirrel won't pull out. You can also foward tie the squirrel and reverse it over into the wing but it makes for sloppy heads so I don't do it much
I haven't fished any of them yet and probably won't for a couple months yet, but the technique in the global flyfisher link I posted earlier seems to do the trick with holding the hair securely and it still allows for a "not too sloppy" head.