I find the metallic sprays from GW tend to be a little on the transparent side, so an initial undercoat of grey helps.

1. Prime with Mechanicus Standard Grey
2. Prime over that with Retributor Armour

Gold (Armour Trim)

1. Base with Retributor Armour
2. Shade the recesses with Agrax Earthshade
3. Highlight sharp points and fine edges with Stormhost Silver

Bright Red (Armour Panels - Forearms,Shoulders and Shins)

1. Base with Mephiston Red
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Evil Sunz Scarlet
4. Finer highlight with Wild Rider Red
5. Highlight fine points wiht Fire Dragon Bright

Dark Red (Armour Panels)

1. Base with Khorne Red
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Wazdakka Red
4. Finer highlight with Cadian Fleshtone

Grey (Armour Ribbing)

1. Base with Mechanicus Standard Grey
2. Shade the recesses with Nuln Oil
3. Highlight the edges with Dawnstone
4. Highlight fine points with Administratum Grey

Black (Cloth)

1. Base with Abaddon Black
2. Highlight the edges with Eshin Grey
3. Highlight fine points with Dawnstone

Tan (Wraps)

1. Base with Rakarth Flesh
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Rakarth Flesh

Bronze (Details)

1. Base with Balthasar Gold
2. Shade the recesses with Agrax Earthshade
3. Highlight the sharp edges and fine points with Stormhost Silver

Blue (Lenses and Cables)

1. Base with Sotek Green
2. Shade the recesses with Drakenhof Nightshade
3. Highlight the edges with Temple Guard Blue
4. Finer highlight with Baharroth Blue
5. Point highlight with Baharroth Blue mixed 1:1 with White Scar

Brown (Leather)

1. Base with Rhinox Hide
2. Shade the recesses with Agrax Earthshade
3. Roughly highlight the edges with Skrag Brown
4. Finer highlight with Ushabti Bone

Bones

1. Base with Zandri Dust
2. Shade the recesses with Agrax Earthshade
3. Layer upper surfaces with Ushabti Bone
4. Highlight along the edges with Screaming Skull