Oh yeah, Mr Schell is incredible.
The film industry is one of the biggest employers of sculptors. Most of the work you'll never know is sculpted, that's the point.
Full scale busts are often taken from life casts of the actors, or sculpted side by side as a reference. Life casts capture every bit of detail (sometimes pulling out an eyelash or two that embed in the cast just as it sat on the person). Every pore, wrinkle, fingerprint, etc. is perfectly preserved.
Again, that's not to take away from an extremely talented artist at the top of his game. And this one is not necessarily from a life cast or one used as a reference, I mention it because it's the fastest way to an accurate result.
The end product is most likely silicone. It's used widely now in makeup effects and props. Back in my day, we used pharmaceutical gelatin melted with glycerin instead. It offers the same translucent effect, pliability of skin as well as being able to punch in individual hairs to mimic the real thing. These days silicone has advanced to where it can be used the same way, but with better results and longer lasting. I have slides of Dick Smith's work on Ghost Story of a gelatin head of Douglas Fairbanks Jr that side by side with the actor, you could not tell the difference.
The eyes also help, today you can get acrylic eyes matched to the actual subject as well.
