I do a lot of sculpture work (never tried bronze yet), and I've always had problems with armatures because of the shrinkage of the clay over a stiff frame makes it crack. (One reason why I've never gone much bigger than about 24".) Maybe I just need to learn more.
Do you usually end up doing your pieces in bronze, or fired clay? (I love your dancer piece!)
Several of my pieces are ready for bronze, but I have not yet bronzed any. I think you just need to use the right kind of clay. You shouldn't have shrinkage issues with professional grade clay. However, you will always fight your armature, so the more you can plan it out in the beginning the better. To do larger pieces you usually have to weld together steel bars or rebar. So I usually do a rough of a smaller piece first to figure out how the armature will look then weld the steel armature together.
I really liked your WIP photos of the dancer, and how you started out with almost an entire skeleton. That's REALLY paying attention to the anatomy!
Guess I'll just have to try it again. My previous experience was with smaller pieces, so there may be something with larger bulks. I also know you used foam in one place, which would have the ability to compress as the clay shrinks. I can also see the "fighting the armature" point. I tend to tweak positions a lot as I'm sculpting, so planning it out ahead of time is going to take some real discipline, and an eye to visualize the piece. Yeah, I've seen some of your test pieces, and can see how they would be invaluable.
(I use all professional grades of clay, but I still get up to 20% shrinkage. I may need a higher grog content, or perhaps even mixing in paper fiber to reduce shrink. )
I am mostly self taught. However about 18 months ago, I started attending a sculpture studio once a week where they bring in live models to sculpt from. They also have some great sculptors like Deon Duncan, Craig Varner, and Dennis Smith. I'd like to think some of their talent rubs off on me. I can tell you with this piece, Deon Duncan cared enough to rip it apart the first time she saw it. Now it is much better.
You can get the clay for around $10 per pound. There is probably 4 pounds so far. Then you just have to buy the armature (in this case steel threaded rod from Home Depot) and a wooden base. I also have a styrofoam ball in the center of the head. So it depends on your definition of expensive.
Super Sculpey is polymer clay that you can bake at 275 degrees and make hard as a rock. You can use whatever kind of clay you wish, but ground clay won't have a consistent texture so working it will be difficult.