Go to Supercheap Auto and buy some VHT or Holts brand plastic primer mate, it's designed to stick to flexible plastic parts, and if you've scratched up your sidies, get some high build primer of the same brand.
Once you've primed it, mist a coat of contrasting color over the primer, let it dry, then wet rub it back with 600 grit with a drop of dishwashing detergent in the bucket of water. The contrasting color will highlight all the scratches etc, and allow you to rub them out. This is called "Color Sanding".
More high build primer might be required to fill all the imperfections, or you can buy a tube of scratch filler if necessary. Cheers, Terry.
