I used a product from High Temp- Leveling Polish Compound. Comes in two flavors, heavy (for heavy oxidation ) and light for buffing out light swirls. The are designed for pain, are clearcoat safe and the light will not harm plastics. I polished on mine and they cleaned up considerably, but they didn't look brand new. I think some of it is the effect of sand and gravel and would not polish out.
Kev