About my tecnique , basically I use 2 different ones:
THE FIRST ONE
1- Resin and fiberglass. It is the one I used time ago, and now I use only sometimes. I build the structure in rigid urethan foam, or metal, or what helps me the best, then I work with wax clay. I made a silicon mould with rigid shell (plaster bandages or fiberglass) and I cast it in fiberglass.
Finally, I clean all the edges and repair the imperfections with gelcoat or epoxic clay, and I paint it!
Below, you can see "Gordo" during the mould process: the pink is just acrilyc spay to help the removal of the barrier (division between the parts of the shell). It is a 6 parts mould: it is built in "rings": legs, bust, head, each in 2 parts.
Here the front of the legs is covered by silicon rubber.
Here a coat of silicon on the face!
Here the recent opened mould of Mushroomoon (first picture), with the clay model half destroyed... and the resin cast (second picture) while I'm repairing it with putty.