I just happened to have an extra, so I asked him for an example picture. I was provided with this:
Step 1 - Prime the model black. I used Vallejo Poly Acrylic primer, and shot it with my airbrush. After it was dry, I decided to tackle the black armor first. No, normally, you can go with a grey extreme highlight, but to do this you have to have tons of brush control, and even then, the highlights look wonky to me. I decided to give this one a shot of the old "off black" treatment. An easy way to quickly highlight black that will give the black parts some color variation.
I took P3 Coal Black, and mixed it 50/50 with GW Abaddon Black. This was applied in a drybrush over the whole of the model. I then, added more P3 Coal black (about a 75% Coal Black to Abaddon), and drybrushed again, going lighter this time. The last really fine, controlled drybrush was with straight P3 Coal black. Alternately, I could have just applied a straight up light drybrush of Coal black, and then used Nuln Oil wash to tone it back.
Step 2 - Color blocking golds. Using GW Retributor Armor, I blocked in the shoulder pad trim, shield trim, and various other bits and bobs. I applied GW Mephiston red to other trim areas, like the hair, lappets (the strappy things hanging over the codpiece), and hammer grip wraps. After this dried, I applied a wash of GW Agrax Earthshade.
Step 3 - Color blocked out the GW Naggaroth Night on the shield, shoulder pad, and the rear tabard. I also applied GW Ironbreaker to the hammer sigil on the shield and shoulderpad, as well as the head on the hammer. I went with this as I wanted a brighter steel than Leadbelcher. Once dry, I applied a GW Nuln Oil wash to the purple and silver areas.
Step 4 - I went back to the gold trim, and applied an edge highlight with GW Auric Armor Gold, followed by a smaller edge highlight of GW Liberator Gold.
Step 5 - I re-blocked out the purple areas with GW Naggaroth Night, and then applied successive hightlight of 50/50 GW Naggaroth Night and Genestealer Purple. To the rear facing tabard, I applied both GW Naggaroth and the mix in successively lighter drybrushes.
Step 6 - I then followed up with a very fine line highlight of GW Genestealer Purple. The final drybrush on the back tabard was with GW Genestealer Purple
Step 7 - I then started blocking out the lightning bolts on the shield and shoulderpad with GW Mephiston Red. I painted the scrolls in GW Dawnstone. Once dry, I washed with Nuln Oil.
Overall, fun to paint (I really like the color combos on this one) and pretty simple! Enjoy!