Wow, I've been at this for ... eh.. lets just say longer than I like to mention around teenagers for fear they realize I have sculpting tools older then they are. ;D Anyhow, I've been at this a while, and I'm still learning plenty here. Great thread!
What can I add? I've always felt pretty strongly that material choice for sculpting medium should be influenced by the nature of the object being made. If you're sculpting something organic with rounded edges and smooth transitions, clay is most appropriate. If making something mechanical looking with hard edges, it may be best to carve your master from wood or build it up with rough clay sculpt then mold and cast it in a hard material for final finishing. There are exceptions to the rule of course, and this certainly is just one approach.
There are a number of books that have helped me over the years with sculpting and mold-making instruction. I'll just list a few here. I had
"Grand Illusions" by Tom Savini when I was in my early teens and the experience of reading and trying many of the things I saw in that book was invaluable. It teaches by example sculpting and in easy language the techniques of mold-making, casting, material choices, prosthetics, life-casting, denture-making, and many other practical techniques I still draw on today.
Another excellent sculpting instruction book that helped me greatly very early on was
Modeling the Figure in Clay by Bruno Lucchesi. It's an amazing step by step guide to sculpting anatomy. Through the book he sculpts a uncannily realistic figure bone by bone, muscle by muscle until he ends up with a female nude so lifelike it looks like it could step off the pedestal. The he sculpts it stepping off the pedestal for realz. O.O It's tremendous.
Another great resource I didn't find until much later in my career is
The Prop Builder's Molding and Casting Handbook by Thurston James. This is one of those 'I wish I had found this book 10 years ago' books. Much of the technique is review personally, but only because i didn't find it earlier and it still has plenty to teach me. It is an older book, written in the 80's and the examples are a bit simplified, but the step by step technique, illustration, and range of subjects makes it a fantastic resource. It covers mold-making, casting, and vacuum forming for theater props and small sculpture. I had already been vacuum forming for a few years before I came across this and it still answered many of my questions.
Lastly, I'd like to impart some advice. Don't underestimate the value of hands-on learning. All the Q & A and reading, and resource gathering is excellent place to start, but you have to train your hands as well as your head. There is a sensitivity and tactile sensory nature to this, and you have to develop 'the eye' for it. It can be facilitated by research, but has to be learned by doing. Sculpt as much as you can, one project at a time. Immerse yourself in it, and the skills aggregate much faster than if you just try it out every once in a long while.
Hope that helps.
