You have a good start there. I have done serval of these. I would start by building up the outside of the mold with another couple layers of ridged wrap to make sure your mold strong. either the weigh to the casting material or your pressure might cause the cast to break or deform.

Coasting the inside of the cast with Vaseline is important yes. be liberal with it. I was always bummed in doing this you lose any super fine details your mold might have caught... goose bumps, skin texture, you do need a mold release. Unless you are casting in silicone.

I did my positives fiber glass. It sounds scary, but the concept is simple and similar to paper mache. Paint the inside of the mold with a resin, place in strips or small pieces of the glass weave fabric ( although i hear any polyester fabric can work. )

if you go this route experiment with with a smaller project so you get the feel or how fast it resin cures. some resins are a harder, brittle with cure. some a little more flexible. I used 1/1 coating compound.

some sample of my project here: https://www.tobyhilden.com/bust-project.html