The metal on the rocket was created using a flat metal image then transformed to match the contour of the rocket. After I have the texture set I go in and apply light and shadows with the layer blending mode set to overlay for the light sources and multiply for the shadows. After the texture and the lighting is set, go in with a grunge brush and add a small amount of dirt and grime to give it a bit more of a tangible look.

The final result of this can be seen at: http://www.zoowee.com/campaigns.php

I know not the point of the article but the metal finish on the rocket is amazing! Love to know how you achieved it.

Looking forward to the follow-up!