u/Jadehorror

Hello!
I'm currently making a custom doll based on the Mushroom Mycelium Naming Series BJDs- I got a pack of accessories from kikagoods that came with a head base, and I'd really like to make a (preferably reusable) mold of it so I have multiple blank pieces to work with for the faces (it comes with unpainted hair, but they aren't suited to modify into the design I want)!

I've tried a basic two part mold (top+bottom), but I haven't had luck using it to cast (because well, gravity. Gravity doesnt play very well), does anyone have any suggestions?

(While this looks like a nendoroid head, its much skinnier and I haven't been able to find any existing 3d models either because its a rather niche doll, I truly appreciate any help or suggestions)