If it were me, I'd sculpt the piece in a harder wax based clay (I like Chavant) then mold it in silicone and cast it up in resin. Then maybe sand it down and polish it, then mold it again. That's me though, lol. The materials are easily accessible but can be pricy. You wouldn't need a whole lot of chemicals, so If you wanted to go that route, I would just get like the sample quantity. I would use Hard Chavant clay, Silicone GI-1000, and Smoothcast 320 resin.
Would love to do that but supplies on this island for this stuff is quite limited. Time is also an issue so that rules out ordering stuff in. The remolding of a cleaned up cast is something I aim to do. Thanks so much for the grocery list though, definitely going to give those a look. Astounding work with your android sculpt, love seeing original pieces.