There's some metal gradient effects in photoshop which can be applied to the car sides, hood and roof, and blended in with a base coat of grey-blue and grey-purple. This gives you about the best chrome-like effect you can get with the skins. The base coats only need a touch of colour with the grey, I tend to use the Render>clouds option, then cut out the sides, to, front and rear from this and add a grey-white-grey gradient set on MULTIPLY, to each separate section.
A metal-flake effect can be achieved by using Photoshop's NOISE function.