I circled back to dry-brushing over black primer for these, simple and effective!
Before
I got the Battletech: A Game of Armored Combat box for my birthday a few years ago; it included all of these minis that I love.
After
I primed them in black, then dry-brushed color, and then dry-brushed a little white for weathering. I regret the white, but I was still so proud of these paintjobs that I'll never re-paint them.