I personally believe in "Paint over Metal" or Paint-on-Paint, but plastic being flexible will have the paint flaking off in no time.
Metal is also flexible - even elastic to a certain degree.
I have seen Professional Paint-on-plastic projects that look stunning, as long as you don't touch or use them. If you paint on plastic, then I'd use a tonne of clear coat to prevent flaking.
Have you ever thought of laminating it with glossy colour foil - like they did it with cars recently?
Oracal Car Wrapping Cast
