This is a method I experimented with and found that it worked quite well to produce a fast and effective gold colour.
What is so special about this? Well, if you ask me I honestly think it looks a little Non-Metallic Metal (NMM). And that seems to be the hype painting style most people are into. Which is a really good thing as it really pushes the painting skills of any painter that much higher.
I painted this using both metallics AND non-metallics. Let's see how I did it.
First I sprayed the model with flat black. Then I gave all gold armour areas a heavy drybrush of Mithril Silver. After this I proceeded to give the model it's first heavy coat of Gryphonne Sepia wash(GS). Once the GS was dry. I applied another heavy coat of GS. This was repeated till the model has been coated with 5 heavy coats of GS.
At this point the model will start to look brownish/gold. Just the perfect gold look!
To finish of the model I simply hard-edged/line highlighted the "gold" armour with Golden Yellow.
That's all. It should take about 30mins painting the gold on a SG model. (minus the drying time of course!)
And it's a damn short amount of time required to produce a fine looking gold.