Not to step on OP's toes, but I used to use 3 turns wrapped cellophane wrap. It gave a thin protective layer for the finish and allowed speedier clearance on the draw. Some used to use simple left over WalMart bags.
Trigger guard was protected by the cellophane. Shooter_john's black holster looks more formed so he may have used something thinner, possibly a "blue gun" for molding?