I have a male seat mold made from a plaster cast of a Valley seat. It's epoxy and fiberglass coated. I've lent it out and it always comes back damaged from people who have used mold release wax and have "experience" with molds etc. PVA mold release or wax is no guarantee that your casting is going to slide off the mold. I've seen fiberglass shops who do it regularly with hammers trying to get the castings off.

Now what I do with my seat mold is apply a thin coat of Vaseline. Then I lay a layer of Seran wrap over it. The Vaseline makes sure it doesn't slide or lift up. Once I lay up the glass I watch it carefully and pull it off once the epoxy hardens. If you go away on vacation, you may never get it off as the epoxy gets rock hard and shrinks. The seran wrap may produce a few wrinkles in the casting but I fill them with epoxy putty and sand it out. I mix graphite in my mix to make it black.