Battle damage on gold?

[Firepower]

So, when it comes to painting battle damage on basic colors, the formula is pretty simple: metallic paint, surrounded by a slightly lighter shade. However, the DIY Chapter I'm currently planning has an abundance of gold armor, and I'm not so sure how to do battle damage on metallic colors. I'm planning on making these guys pretty war-weary in appearance, so being able to replicate a butt-load of damage is key.

[winterdyne]

Scorched brown lines with mithril silver highlights for scratches. Larger chips can be done in trompe l'oeil similarly - shade brown at the top, highlight under.

[Hemal]

Gold is a solid metal - I presume that "gold" on marine armour is either gold plate or something that resembles gold in colour, and hence would be uniform throughout. Looking at some of the Veteran minis from the 4th Ed COdex era, they have battel damage on components that would probably be painted Gold on UM 2nd Company, so look at these modles possible for inspiration - however it is entirely feasuble to simply add a wash of scorched brown and black in the pit, and a glaze around the pit of teh same colour, to indicate blast damage when the impact hit and scorched the area or coated it in oxides.