To reiterate what has been said elsewhere but should go here as well, all of Greene's productions are excellent. The portrait drawing video of course will have the greatest depth on that subject, but the pastel and oil videos also contain the basic drawing information and theory discussed in the drawing video.
Greene said in his workshop that he doesn't worry all that much about "likeness", that getting a likeness was actually not all that difficult. There is lots of work to do before you start worrying about getting a likeness, and his videos take you through it.
Curiously, there's no website that I know of to get information directly from him. Contact him at Studio Hill Farm, Route 116, North Salem, NY 10560. Various distributors such as
www.art-video.com carry his tapes.
Some of the best return on your dollar anywhere for this kind of instruction.