One of the bits from the Eavy Metal masterclass was being shown how to get extra contrast in your metallics and make them look more realistic than simply slapping a wash over the top. Some master painters can achieve insanely good looking armour with non metallics, which is a style called NMM (non-metallic metals). I've still not managed to master that one... it's really tricky; mode on that one later.
This style is based upon that, but uses metallics and washes to much greater effect and is referred to as MNMM: Metallic Non Metallic Metals. Again, I've still not quite got the hang of it yet, but the general theory should be pretty clear.
For this we're going to take the Inquisitor that you saw in an earlier post and detail the gold on his armour and staff. Normally you'd see people paint the gold directly over the undercoat, give it a wash of Devlan or sepia and possibly a small highlight of a lighter gold. It looks fine in rank and file troops, but not quite so masterful on characters.
The starting point for gold is getting a nice smooth base coat. Gold paint is notoriously bad for going on smoothly, so you've probably noticed you need a few coats and it end up blobbing everywhere? The simple answer to that is to mix (50/50-ish) in a dark reddish brown, such as the GW Scorched Brown, for the first layer. The non metallic paint particles mix with the gold and help improve it's coverage and evens out the gold particles, which want to clump together. This also gives you your deepest shadows.
Cover this with a wash of sepia ink to provide a richer finish and hide any inaccuracies in the mix. Once the wash has dried, we can start blending the colours back up to your original gold colour before you mixed in the dark brown. For me this was probably only two steps; first start with your original mix over the wash, leaving the darkest recesses untouched; then reduce the mixture to 75/25 Gold/Brown and then pure gold.
Once the golds are done, paint some very watered down Scorched brown into the shadows, followed by a 50/50 Scorched Brown/Black mixture into the deepest recesses and shadows.
The final finishing point is a very thin highlight of pure silver to the edges.
That all sounds rather complicated, yes? I think the gold on the Inquisitor model above took 10 minutes in total as the blending works best when it's all still wet... so it's a lot easier than it sounds. The important thing to remember while painting in the shadows and highlights are to think about your light source so the shadows fall naturally on the model; but that is for another article and something I still need to work on myself.