Honestly, people make crayfish flies way more complicated than they need too. A hook with some dumbell eyes, some sort of claws (either small strips of rabbit, suede, foam, or hackle), a palmered hackle body and some dubbing will catch as many fish as a fancy one will. You should be losing flies fishing craw flies if your doing it right, because that's where the craws are actually living.
If you want a fancy looking one look up Brian Wise's video on Duane Hadas Creek Crawler. Dally's has the video a few months back on their blog, and you don't NEED the epoxy coating, but it does make it look better.