In case anybody was wondering, the expressiveness of my animated heads is going to be pretty low. A bit of a weak spot in the film. But there ain't that much I can do about it; replacement heads isn't much of an option (probably using HDR photography, which shows up every little texture variation that isn't even visible to the naked eye). And what i'm doing already is ambitious enough for the time I have. Almost too ambitious; seems a little naive in retrospect that I thought I could whip up an animatable head in a short period of time. And none of it is turning out to be easy.
I'm going for an opening and closing mouth, at least, and moving eyeballs. I'm attempting to make animatable eyebrows, but I might have to go back to plan B, which is adhesive backed eyebrows that I can move around on the forehead. I'm also going to feel out the possibility of more movements around the mouth area, but not sure how successful that's going to be.