For climbing supervision skills and boys who have earned their first lead award, we use David Fasulo’s Self Rescue book, part of the Chockstone "How to Rock Climb" series. This provides a relatively complete set of skills and exercises for handling technical climbing rescue in a manageable format. We’ve found that actual practice of these skills is a bit of a rope management nightmare (in part because of additional safety lines), and best done with more than the usual amount of deliberate caution.
To that we add basic instructional techniques and supervised teaching practice. Since one of our number teaches in the University’s education school, we rely on that and don’t have any specific "how to teach field skills" materials generated in-troop. (OK, OK… one of these days we’ll write this up…)