Did the paste wax have a silicone additive because that will tend to inhibit the curing process of polyester resin and leave it tacky. If you check out the Fibreglast website, they have a mold release paste wax by Partall that is silicone free. They also have what most people use as a release agent...PVA or aka PolyVinyl Alcohol. Usually sprayed on right from the bottle without diluting and at a higher pressure than what you would use to spray paint. Usually about 3 or 4 coats one after the other (it dries quite quickly).

As for the plaster mold, it would have been a good idea to use something as a seal coating on it like perhaps some form of primer coat, like a catalyzed primer. Something to seal the plaster and give you something to sand down to a finer finish. Also, I think the plaster would absorb that PVA and you would need to use the wax first to prevent the PVA from soaking in too much and not working as a parting film.

Check out the Fibreglast website at http://www.fibreglast.com/ to see what is available. Good luck and good flying.