Perlman's book Basic Clawhammer Banjo is anything but a basic clawhammer book--it contains tablature for a few dozen fiddle tunes, few of them part of the repertoire of most bluegrass players. The latest edition of that book comes with a CD of one time through each of the tunes (just AB, not the traditional AABB) with no accompaniment. To give an idea of how far from basic the book is, the first song includes triplets.

Perlman does have another book, Clawhammer Style Banjo which is a basic text. There are both audio and video tapes available for the lessons in this book. Pedagogically speaking, the video tape is extremely useful, showing clear closeups of both hands (esthetically speaking, the tape is one of the ugliest I have seen). The song selection in this book is much more useful than in the other book.

When you play up the neck, although you go physically lower, you go higher in tone. That's why it's called "up the neck." Some clawhammer players use finger picks--backwards, of course--and a thumb pick, both to protect the nails and to get greater volume and crisper tone. I've never been quite comfortable with them, but i've also never been very comfortable using picks for three finger picking. For a while, I was going every week or two to a manicurist to have the nails on my index and middle fingers built up because my nails are not very thick, but I stopped it because the manicurist was filing my nails almost down to the skin before applying the polyester or whatever it was. I stopped doing that because I stopped whamming on the strings and head as I learned drop-thumb (double thumbing). I sometimes put scotch tape on my nails before a long session. It works for a while, and can be easily replaced.
Again, I strongly recommend the book and video from Ken Perlman. --seed