I dunno what type it is other than just regular sculpting, I just made a skeleton out of wire to give it some framework then just flopped it on in the rough shape I wanted then started adding detail with an exacto knife, a toothpick and a looped over paper clip then smoothed it a bit with my pinky
The stuff is a brand of super sculpty called "sculpty III" I got at hobby lobby, its quite soft and mallable and doesn't dry out or harden till you put it in your oven at 400 degrees I believe. I think you can sand it a bit afterward.
Stuff like the shoulder armor and straps I made out of little bits of sculpty and carefully pressed it on.
I wanna try and make several, and maybe sell a few custom ones at some pounce depending on how well they turn out. Gonna paint it once its all baked. Just wish I had an IRL game to use it in.
If you do any be sure to post 'me up!