I've used crayfish for largemouth & smallmouth bass, and they have worked spectacularly for me at times. I like to work them on a wide-gap number 6 or a non-barbed baitholder hook style size 4. In terms of rigs, i stick to 6 or 8lb trilene xt low-vis green, and i use a split-shot rig, with one small split shot about 1 foot above the hook. I hook the crayfish through the tail, in the middle of the tail, with hookpoint coming up from the bottom of the tail to the top. I fish the crayfish by lobbing it to the desired spot, and letting it slowly sink on a semi-taught line. I like to fish crayfish to specific spots ie: above water ledges, bridge piliings, rocks.
I will also use crayfish under a float if the bottom is particularly snaggy.