So I told my husband that I'd like help making a duct tape dressform. He looked at some of the info I had bookmarked and said sure. But he had a better idea of how to do it. We went through the standard procedure, but with a garbage sack under the tape.
So after he cut off the duct tape form and slathered the inside with vaseline, he used it as a mold to contain expanding-foam insulation. He even put a T frame of pvc pipe in it so it could be put on a stand.
Making a dressform of yourself is certainly one way of discovering your body flaws. Yes, appearently on of my shoulders is higher than the other. In fact, most of me seems to be off-kilter.
A few months later, after my son complained about "that thing standing around naked," I got around to covering it. I used a couple of old undershirts for the fabric because they were thin, stretchy, and available.
Most of the cover was shaped by pinning while on the form, then basting, trying back on for fit, then serging.
To fit the bust, I cut the cover off a couple of inches underneath it. Then I split up the center. I made horizontal darts, then closed the split, and added darts vertically up from the bottom edge.
It was at this point that I realized that fitting it inside-out wasn't good. Because when I turn it right-side-out the shoulder fitted to the right side would be on the left shoulder, and on down the line. But I decided to press on and trust to the virtues of stretchy knits. (That'll probably come back and bite me in the butt later--which is probably also lop-sided.)
I added a dart up the back. Finally I added the middrift section, which I also shaped to fit the hips. I'm going to run a cord through the hem at the bottom, so I can cinch it in tight.
It's not pretty, or level/plumb/straight. But it's just the form and cover, not a dress.
EDIT: I've added clarification of how my husband used the expanding foam and the duct tape "mold." It's at the bottom of page 2. (I was so proud of how I figured out how to cover the dressform, but more people are interested in how he made it. I'm cool with that.)