Look at this! So, Latex, right... that stuff, I had to actually remember how to make it work the way I needed it to, and to again, have patience with materials that need to DRY. (dope slap's Mac from the past.)
ANYWAY, Latex in small amounts is an effective makeup material, it can be used for aging, small cuts and creating wrinkles. But it can also be used as an agent for the Halloween masks.
So once I finished my mold I poured about 1 cup of latex into it, and rolled it around inside. then filled the rest of it. I had a few little leaks but those sealed themselves quickly enough. The latex was allowed to dry over about 24 hours.
The leaks create an edge around the mold called 'flashing'. This needs to be cut off the newly formed and dried latex head, but this can create a seam, which needs to be filled with a glue of some kind, in order to make a smooth edge.