It’s not an easy job, if you’re into model making and have an airbrush then you’ll have probably had a go at a convincing natural metal finish at some point.
Preparation is very important, a metal finish is very unforgiving of the slightest blemish and even then, metal effect paint isn’t very durable and doesn’t take well to lacquer.
For best results, spray a layer of a primary gloss colour onto your plastic, gently sand any blemishes with 1200 grade paper and recoat with gloss. Once dry, you can spray with chrome effect paint, but because you’re spraying gloss on top of gloss, there’s very little “key” for the top layer to attach to. Although you may find that the chrome paint will rub off to the touch.