Try some of the new washes, they work really well on toning down some shades, in particular metallics and skin tones. They'd work well on Grimgor especially.
i know this now as I am working on some Blood Angels (the new washes are amazing!), but i was just wanted to show you guys these old orkies s you can compare my work from 7 years ago to my new ones
I might re-do these at some point though