Seeking more info on “skinning”

I’ve been watching a Scott Robertson technical sketching DVD, and just learned the basics of drawing a form’s silhouette, AKA “skinning,” after drawing the form’s cross sections. I’m looking for details on skinning, including any theory behind it, but I haven’t come across this subject in my drafting or fine art drawing books. What books or other resources could you recommend to learn more about this subject?