Not that I really ever use Krylon or Rustoleum these days (except the Krylon Short Cuts occasionally for all purpose work). But if you are going to use that big can stuff you nearly ALWAYS need to use a primer to protect the plastic. I painted the turquoise portion of this 58 Impala with Krylon back in 1995 (it's a former box art car for AMT/Ertl, which is why no windows.

And in 2000-ish, I built this AMT Trophy Series box art replica using again, a base coat of gray primer, Krylon White, and Krylon Red. Today, I'd use Tamiya. I think they've reformulated Krylon paint a few times since then, and last time I spoon tested (with primer) some Krylon I didn't love it, but you can get away with using the stuff.