BTW, Humbrol 117 is the same as RLM 82 (for those EU & AUS guys).
@F4R, the way I see the helmet was painted at the DOME is, first primer (Ok, I know

), then the silver (a really bright polished silver), the the grey applied on some spots (so it goes from heavy grey to light grey at the same spot, as can be clearly seen at the pic above), the the green coat, and last a dusty grey all over the helmet, heavier at some spots. And then, why not, a light acrylic black wash.