Open Question: Painting coleman coolers?

I'm having trouble painting my coolers. I bought 2 Coleman coolers from walmart and they are both blue. I got white krylon plastic paint and have sprayed 2 coats and it looks like its sticking fine and when you rub your hand over it its fine but then if you take your fingernail and barely scratch the surface it just flakes off like that. Would a clear coat fix this? or am i screwed?

Source:
http://answers.yahoo.com/question/index?qid=20110322084751AADnqcs

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