Yes but you would need to apply the Fibrecoat PU Primer and let it dry to ensure firm adhesion of the resin to the trim.

Apply the primer manually via roller or brush as a wet film to the surface of the GRP roofing trim and leave for around 15 minutes to cure. The primer will evaporate leaving a matrix of molecules activating the surface of the trim. After the primer appears dry, apply the Fibrecoat base coat.