If you are talking about the vodaphone car you will want to use either plain silver (easiest can just buy a rattle can) or airbrush with Alclad chrome for lexan pn alc-114 (hardest will need airbrush). Alclad makes chrome for plastic which is part number alc-107, im assuming this is used for painting outside.
The problem with this chrome paint is surface prep. You would have to prep the rear wing with black to basically mirror flat for the chrome to be chrome. That stuff is extremely fine and even the smallest defect on the starting surface will show horribly.
With your horrible painting skills I would just stick with some tamiya or pactra silver and call it a day!