BSeed said:

"Some clawhammer players use finger picks--backwards, of course--"

That's the cart before the horse. Clawhammerers wear the picks with the picking surface over their nail (one of them), as God intended. Bluegrass players are less efficient, and have to use three plus a thumb-pick, probably because they make the mistake of wearing them backward, with the picking surface over the fleshy part of the finger, a great heresy.

Dave Oesterreich