I have made some dress makers dummies in 1/4 of life size. First I made a body out of paper clay after a measurements chart for a size 38 C (European size) when it was dry I covered it first in saran wrap. This was really stupid since this made my mold all bumpy inside :/ If you are not going to use the body for anything I would lacquer the paper clay body and then put a thin layer of paper clay over that and then put out papier mache over that when it is all dried.
Then I covered it all with papier mache to make it all stable. When it was all dried I cut the papier mache in two parts so that I had a front and a back and then I painted it all with liquid latex.
When dry I duck taped the two parts together and than it was just to pour the plaster into the mold and wait for it to dry, I also put a old wine cork that I had duck taped in the bottom of the dummy, to make a hole for a “foot” to be attached to the dummy to make it actually stand up.
When the plaster have cured one just take away the duck tape and the cork and pop the dummy out of the mold. The you clean up the seams with a knife and put it somewhere to cool down. The plaster can become quite hot when it is curing.
Since my dummies ended up bumpy I also sewed fabric cover for them. Now all they need is feet and then they are totally finished. The good thing with having a mold is that one easy can make lots of identical things.