Thanks skunkwerks and to all who helped. PY is a treasure.
I saw no reason to clearcoat them but appreciate the warning. I will also try the toothpaste next round and wax is a good plan.
I just spent another hour on the first two and am now calling it good enough. I have a couple more when I next get bored.
I was basically using too much polish, spinning too slowly, and pushing too hard. This Meguiar's M105 worked well with the DA mode on the polisher and left a uniform scratch:
This is what it looked like after that M105 and my failed polishing attempts:
After using a new soft foam pad, straight spin/no DA, light pressure, high rpm, and just a little Novus #2 polish, they cleaned up a lot:
I invested enough on these tired parts, learned some stuff, have a new tool, and will move on to bigger challenges!
Mike