[Azur]

I think with 300 grit you will go trough the underlayer. I would use a Trizac 1000 grit wet instead. As a compound I use Rupus blue, with the blue pad and after that Rupus yellow co.pound and yellow pad. Still, depending on the surface amount, why not concider sanding down if needed, re-primer, add the new coulour layers and finish with the new clearcoat layers? Could be done with rattle cans if you use proper quality lacquer. But for appr. 200 pounds you could let it respayed professionally for optimal result and save a lot of time and effort.