I have an aftermarket spoiler that that I am refinishing. After doing some research I think it is SMC fiberglass, but one can never be sure with aftermarket... The material is white and it does not float in lacquer thinner, but it doesn't melt or soften either. What is the best prep before epoxy primer? Is ad pro needed with fiberglass and/or the thermoset SMC resins? Since I'm not certain of the material, would I error on the side of ad pro or not?