For deer and elk hair, I always use the neck. These are significantly better quality hairs for tying flies. As mentioned, when preparing the hide, use a sharp knife at a 90 degree angle and scrape until you can't scrape no more. I prefer using pickling salt and seems to work fine. Definitely, wash with soap before and after. Never had problems with bugs.
Also, don't forget the tail of a whitetail deer, great tying materials.
For birds, same process, there usually isn't as much meat and fat on the skin and it is a little more delicate.
I have had some good success so far and could give up some elk and deer hair, if anyone is interested. I will probably have 2 full deer necks and half an elk to give away. My success on the pheasants hasn't been good this year.