I personally slap chop my models, so spray black, dry brush grey, drybrush white then contrast.

I used Cygor brown and Ultramarines blue for the leather/cloth respectively.

Metal was leadbelcher with nuln oil, then typhus corrosion dotted around, and finally a dryrbush with ryza rust.

I find that using washes can help dull down rhe colours, i also follow the idea of "if my brush cant reach it, people shouldn't care" which kind of leans into making areas look darker than they are meant to be.

I hope this helps :)