Complex sentence: Méliès himself sculpted prototypes for the heads, feet, and kneecap pieces in terra cotta, and then created plaster molds for them; a specialist in mask-making used these molds to produce cardboard versions for the actors to wear.
Split into simpler sentences: Méliès himself sculpted prototypes for the heads, feet, and kneecap pieces in terra cotta, and then created plaster molds for them. A specialist in mask-making used these molds to produce cardboard versions for the actors to wear.