Making progress but it's coming slowly. Hair is a real tricky thing to make and I'm still trying to find the best way to do it without spending hours sculpting it.
Zbrush is the program I am learning right now. I'm proficient in 3DS Max and that's what I assume the other 3D yukkuri guy is using. Zbrush has a lot of advantages over Max if you want quick, detailed models, but Max and Maya are better for game-optimized models.
I like the mouths with depth but that would take much longer to do in Max. With Zbrush I am able to put accurate faces on them in seconds and change them right away if need be. Not to mention Zbrush has polypaint which allows you to quickly put textures on without UV's.
Fush has a point, but you would only do that for optimized game models. When you're making a 3D movie or still image you use as many polygons as possible.
Hm. I was planning on modeling the generic template for a yukkuri with an actual mouth opening (with a small cavity behind it) and toggle visibility on teeth or tongues as the situation demanded it. Additionally, I was going to utilize this for the eventual yukkuri abuse physics. In the long run, I must keep your heuristic in mind, Fush, as I don't want to bloat potential calculations.