1. I find the metallic sprays from GW tend to be a little on the transparent side, so an initial undercoat of grey helps.
2. Prime with Mechanicus Standard Grey
3. Prime over that with Retributor Armour

Gold (Armour Trim)

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

Green (Corrosion)

1. Layer thinned Kabalite Green selectively to give the impression of oxidation
2. Highlight these areas with small amounts of Nihilakh Oxide

Olive Green (Armour Panels)

1. Base with Deathworld Forest
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Nurgling Green

Burgundy (Cloth)

1. Base with Screamer Pink
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Pink Horror
4. Highlight sharp edges and fine points with Fulgrim Pink

Black (Armour Ribbing)

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

Brown (Leather)

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

Silver (Details)

1. Base with Leadbelcher
2. Shade the recesses with Nuln Oil
3. Highlight the edges with Stormhost Silver

For grenades, replace Nuln Oil with Athonian Camoshade

Yellow-Brown (Lenses)

1. Base with XV-88
2. Shade the recesses with Athonian Camoshade
3. Layer the middle with Balor Brown
4. Highlight fine points with Averland Sunset