Thanks for the encouragement, guys!
I should have listened to Brian Muir a long time ago. Working with oil based clay is so much more rewarding than, say, modifying a Rubie's and trying to force the plastic to do what it doesn't want to do. Fortunately, the years of studying Vader and trying to rescue crappy online purchases have helped develop an eye that causes my clay sculpts to benefit.
I don't have a game plan in terms of what specific products to use to mold it. I've since done some additional domework on the fiberglass projects (e.g. Goldie, Quasimodo) so I need to port that knowledge back to the ClayNH dome.
I've also decided that I should really try to sculpt the teeth and tubes into the mask instead of trying to do a first pull and then use two-part epoxy clay (the old fashioned way).