Skeletton and steel parts

1. Base coat with a 1:1 mix of Gunmetal Grey and Abaddon Black (easier with airbrush, if you don't have one, prime with Leadbelcher ).
2. Wash with Nuln Oil .
3. Wash with a 2:1 mix of Nuln Oil and Agrax Earthshade .
4. Drybrush with Leadbelcher .

Metallic details

1. Base coat details with Castellax Bronze , Warplock Bronze and Balthasar Gold as you wish.
2. Wash with Agrax Earthshade .

Black Armor

1. Base coat Abaddon Black .
2. Drybrush of Eshin Grey from top to bottom and left to right.
3. Light drybrush of Dawnstone only on the top of each panel, from top to bottom.
4. Wash with Nuln Oil , applying only as a really thin coat, it should not pool anywhere.