They just need good preparation. Make sure that you apply a good two coats of sealant, plus a couple of coats of wax before they go on the car. They wash very easily, but sadly they don't stay clean for long!
Re the polishing - it's only temporary but Dodo Juice Red Mist Tropical gives them a nice shininess - though I prefer the matt finish.
One of mine is slightly damaged and will probably need a respray. I'm dreading it because I don't think they'll all match.