It's no problem to use an epoxy mould, although if you are doing ambient temperature cures with polyester materials then a good quality vinyl ester tooling system (like Unimould) will last just as long as the epoxy mould, and has the advantages of being much easier to repair and polish up if you ever need to.

Epoxy moulds are great, but really better for higher end component production like pre-pregs.

Hello , im doing a spoiler prototype , i want to make a mould of this spoiler in fiberglass 
I want mould resists a lot of copys , i thinked the best way os  gel coat epoxy  grey  high temperatures for prepegs, fiber glass , and epoxy resin . The copy will be do with top coat poliester , fiberglass and poliester resin. It is compatibility?
Thanks , sorry for my english