There are two types of Polyester resin for fiberglass:
1. Laminating resin .... contains wax that comes to the surface when
curing so that the next layer fully bonds ... the wax is an 'air
inhibitor'. Laminating resins will always feel sticky to the touch
because of the wax. This wax is soluable in liquid polyester.
2. Finishing resin ... contains NO wax and when exposed to air while
curing forms a hard surface

What you have is probably finishing resin .... and any contact with wax
will change it.

So, you cant use wax anywhere near a finishing resin or you'll
contaminate it and begin to turn it into a laminating resin ...... but
you can use SARAN to keep it sticking where you dont want it to.

In article .com,
wrote:

I notice on the bottle of polyester resin I got that it says not to mix
the stuff in a waxed paper cup. It's in bold too, so it seems
important. Not only was that how I was going to mix it, but I was going
to lay the material on some wax paper so it won't get glued to the
floor. I have used 2 part epoxy in this fashion and it has worked well
(the epoxy cures and was too flexible, so I'm using polyester.). Does
wax react poorly with polyester resin?