Once a year, I use Meguiars formula 82 using that Porter Cable buffer mentioned earlier, applied with the foam applicator it came with. Does a great job removing swirls and rag scratches, not that I have many. Meguiars recommends clay-barring the finish before working on it.
Finish on my '69 is basecoat / clearcoat done in 1985. I'm contemplating color sanding and buffing it over the summer. Haven't done that on this car since 1985.