My friend Tawny (who made the Skeksis last dragoncon) is taking a crack at this!
tawnyscostumesandcuriosities (who everyone should follow, btw) will do amazing at this! Tawny’s skeksis is a work of art; look at this hallway picture I took at last year’s DragonCon:
I used the sculpting armatures from Composite Effects:
It is heavy duty enough to cast on (and I believe it’s what CFX uses to sculpt their own pieces on). Just DO NOT get the display head to sculpt on. It’s not solid enough (speaking from experience here).