I started by spraying the mini with Vallejo's bronze as the basecoat:
I then coated the model with GW nuln oil and drybrushed with Vallejo's brass, and tried to highlight some edges with Vallejo's old gold:
In theory, this is fine, but there is a real lack of contrast going on. Of course, when certain bits such as the armor joints, horns, eyes and so on are painted their appropriate colors the minis will look better.
Last week I was at my local GW and found a color I'd never seen before and really liked! It's called Screaming Bell. I thought this might be a great initial undercoat over which to layer the bronze/brass/old gold.
I also used this as an opportunity to test out GW's nihilakh oxide, which I believe is a perfect opportunity to make the paint scheme more colorful without looking like a rainbow. This is my first attempt, and clearly I used too much of the stuff, but here are my results:
Half is just screaming bell washed with nuln oil and then bronze drybrushed over it, and the other half is the same but with nihilakh oxide in the recesses before the drybrushing step:
I think if I use less of the nihilakh oxide and apply it before the nuln oil, the effect will be much better.
Here's a random test plague marine with bonze basecoat => drybrushed brass with screaming bell highlights sprayed on just to see how it would look:
I like it. It's more copper than brass, but perhaps for certain bits of detail and for the purposes of contrast it can add a nice warm color to the model.