Any polyester laminating resin, or other polyester resin materials that have not been fully cured with the use of a paraffin wax, polyvinyl alcohol (PVA), or by eliminating any contact with air, should never be coated with anything besides another polyester resin material (such as more uncured polyester resin, or gelcoat material). Do not apply any uncured epoxy materials to uncured polyester resins with the intention of forming a chemical bond while both materials cure. In certain cases this may work, but there is a reasonable chance that one of the materials may not cure properly.