If you are going to sell this kind of thing, the Internet offers the overwhelming advantage of being able to show samples. In an arts & crafts store, you may have a chance of showing a samples DVD, but my experience with popular stores is that people there are not looking for education in this area.
If this is to be useful to me, it has got to fill the gap between a book and actual hands on, which means it has got to give a very good idea of how hard to hit the rock or how to attack the wood. If it is modeling, it has got to make clear why the choices work. I just saw a video of Ron Mueck making one of his oversized figures (Pregnant Woman) at the Fort Worth Modern and for an informed person, just watching made a lot of choices clear (how much rough work before the detail, how big the manques (sp?). Actually, selling at museums and university book stores might be a better choice.