Even with metallic it's difficult, and you've got to the keep the gun moving, otherwise, you'll get an excess of 'glitter' in one area.
I've seen cars with it on (like green base with gold flakes, it looks mad), but not many. Expect to pay for the job, I can't think of anything more difficult. (apart from spraying acid or something).
Can't you just do like in school, just cover the whole car in pritt stick and sprinkle all the metal flakes over it for (for now).