The first step to restoring old, porous gelcoat is to give it a good wash and scrub. It may seem simple, but it gets dirt and debris from the surface, giving a much clearer picture of the gelcoat's condition. Remove any wax that may be on the gelcoat as well. When the gelcoat dries, if you are able to wipe your hand on the hull and have a powdery substance come off on your hand, the gelcoat needs a full restore. If there are stains from rust, algae, other other residue, products like Davis FSR, Y10, or TotalBoat White Knight can usually remove that in just a few minutes, and without any heavy scrubbing, or wear on the gelcoat.