If polishing is all that’s needed, apply liquid polish by hand using polishing cloths (clean bits of cotton cloth with seams removed will also work).
When using a polishing paste, apply it with an orbital buffer, starting at a lower rpm of 1,400 or so to avoid burning the surface. Rather than apply paste to the buffing pad, place small dabs along the surface to be worked. When the paste is gone, stop buffing, as you can actually mar the surface by continuing to buff with a dry pad.
After finishing with any combination of cleaning polish and rubbing compound to eliminate oxidation, you now need to seal the surface using a polymer polish such as the Star Brite product pictured below. Two coats of polish will provide a season’s worth of protection — though it might be a good idea to do a mid-season touch-up if the boat has prolonged exposure to the elements. If the boat is properly coated in a quality polymer polish, there’s no need to go over the finish with traditional paste waxes. Do a thorough job of cleaning and restoring the finish this year, and come next season, you’ll need only to wipe on a couple of coats of sealing polish, and you’ll be good to go.
Light - Most of the gelcoat will still be shiny, but with a few dull or cloudy patches. A simple oxidation-removing compound should restore the shine.
Medium - The surface is generally dull and shows signs of pitting. A machine buffer and a polishing compound will remove oxidation and smooth the pits.
Heavy - The entire surface is dull and may be chalky to the touch. Pitting is obvious. Extensive sanding and polishing are required, and full restoration might be a job best left to a professional — or call a painter.