I have been using Aves Apoxie Sculpt for a while, I was able to get natural (grey) at a mom and pop hobby shop. Use metal tools, and keep a small bowl of water near by.
Mostly I've made 1/6 scale heads from it with necks made from wire mesh and brains made of paper wads. You want hollow forms where ever possible because it can weigh a bit. I've done best with marble sized amounts of each half and rubbing water on my hands to keep it from sticking to me. I make about what I figure I can work with in an hour and arrived at that amount after some experience. It's easier to make a bit more stuff then wonder what to do with a bunch of left overs. Surface dry time in an hour or so, full cure after 24. You can paint with acrylic paint before it has set.
My work surface is plastic, a small cutting board will suffice, but I dry the heads on a thread spool wrack. While drying you don't want the AS touching anything you don't want it to stick to. They say it's water proof but I was able to chip away at a neck I had made by dipping it in hot water.
A bunch of "don'ts" turned in to a "do". You can see where some of the layers have met and not been blended or feathered together. I also squished the skull just slightly before it had fully set. Some cutting was done with a hand held wood carving set. Things like the teeth were done before it set with a strait pin.
Before and after doing hair in Apoxie Sculpt
