I've tried sanding, torching and primers/adhesion promoters (sometimes all at once) I like the slightly rough, matte look, One reason I prefer to keep the surface slightly "rough" is it leaves lots of tiny nooks and crannies for the primer and paint to cling to.
I've used the below technique on old quads and numerous Barbie Jeeps, Razor mini-bikes and other assorted ride-on toys.
Depending how old and abused the quad is, you may need to scrape in a few places, particularly if it has spent years outside in the sun.
- Sand with a 150+ grit sandpaper.
- Hit it with a torch. This will help burn off mold release chemicals in the plastic as well as smooth the surface out a bit.
- Spray with adhesion promoter/ primer.
- 2 coats of spray paint
Because the original panels are molded with colored plastic, scratches show the same color as the panel itself. Once painted, deep scratches show as the original plastic color. But, they're easy to touch up, and frankly I do this to toys that still have a lot of life left in them, but don't look like it.
