Re: crayfish fly
I second the recommendation of using bead head buggers as a crawfish pattern, they work great if fished properly.
Brown trout are more known for eating crawfish than rainbows are (steelhead is actually the exact same species), but I bet you'll have some luck with them. I would say if the fish are more wild/native and have been returning to that stream (with lots of crawfish) naturally and breeding, crawfish should work. If the fish in the given stream you're fishing are newer stockers, then they may not know what to do with a crawfish.