Fishing Crawfish Imitations For SmallMouth's ?

Hello,

Have a few months to go yet, but fun looking forward to it.
Live in Eastern Mass. Like to fish the Quabbin Reservoir and Deerfied.

Read that Crawfish are good for Smallmouth Bass. True ?
What other species like them ?

If so, how are they fished ?
On the botton ?
Do they come weighted if this is the way to fish them ?
What sizes ? Styles ?

Any hints or thoughts would be most appreciated.

BTW: haven't been flyfishing for quite a while.
What's a "good" low cost source for mail order flies these days ?

Thanks,
Bob