The technique of painting non-metallic metal is used for painting flat areas that are meant to be shiney or reflective without using any of the metallic paints. It's difficult to give a colour-by-colour guide for mixing and painting this effect as it depends on which colours you wish to use. I think it's best illustrated with a picture; take a look at the sunglasses on this Ork Nob...
I used this technique to churn out quite a lot of Deathwing quickly. There are probably better methods, but this technique is all about speed. You'll end up with a cool/neutral looking white. This will work best on armour, such as that of Space Marines or Tau.