So, here are the face plates and brow plates. They are sanded and ready to prime. I used a gesso spray to prime them. I used gesso because it's strong and sandable, and if I have to go back and clean any of these up, the gesso will allow me to do that. I used some cheap clay to prop up the faces, and sprayed three very thin coats.
You can see in this photo that there are a few imperfections around the chin area. After the gesso has a few days to really cure, I will sand these imperfections out and re-prime them.