I usually don't do much painting, spend more of my time building (converting mainly) models for myself, friends, and family. I more or less picked up the brush recently within the last few years. Been painting a friends Iron Hand Marines and the few Tyranid models of mine I've completed assembly for.
Are you referring to the silver of the bolt gun or all of it on the model? For the bolt gun i did a boltgun metal coat with a badab black ink wash, the best i can think of for a highlight for it would be i guess chainmail along some of the edges? I will have to try the gold highlight out, painted it with a mix of shining gold/ mithril silver (1 to 1) then used a devlan mud wash.
I'm liking the crimson color of the robes, to me it suits the model more with the black armor. I did however use blood red on the highest ridges of the cloth then once dry went over those same edges with red gore. I brushed it over the blood red to dull and blend it to the rest of the cloth, but did so thinly enough that the blood red still shows on the higher ridges.
As for the head i'm just going to prime it black and start it anew.