Paint your damage in black and underline the reflection of the light in silver on the lower part of the damage. And you have a 3D effect on your flat surface. Quick and simple.
I've also created a little bit of weathering just to make the armor even more broken looking. I've painted the rust with orange brown focusing the effect on the deep spot (including the fake battle damage).
I've decided to go very easy with the rust because I want to keep my color hue the most colder as possible which is quite incompatible with the orange of the rust.
Enough with the steel metal, it's time to proceed with the golden part of the armor.
Following the same principle than the other color of the mini, I've choosen a cold color for my gold. So pale gold (warcolour) with a drop of black to desature it and a drop of blue to make it colder.
The result is a fondation of pale greenish gold.
Then some glazes of green ink (warcolour) in the mid light area and finally some touches of turquoise on the deeper textured area to create some verd-de-gris.
That's all for today. Next step: the horns.