Hello Paul and thanks, for the metals I used several techniques like acrylics, oils and printer ink, in this case I used first a mix of Black + english uniform, adding lights with golden brown, then I used some oil like raw umber and blak for some tones and shading, for the extreme lights I used Gold printer ink, the gold printer ink also can be use mixing with oils...
hope this helps any question be free to do it
regards
ER