If you're painting 6-10mm stuff, you're going to want to paint on the
suggestion of details rather than actually using the same techniques as for larger stuff... The human eye isn't as powerful as a camera, and can't clearly see details that small unless held right up in front of you. Although you can paint reflections in a 32mm mini's eyes, they won't be visible more than a foot away and will just blur together in the viewer's brain. At 6mm, you can barely see the eyes themselves. So you go back to basics, and paint on simple details that, when translated by the human brain looking at it from three or six feet away, will translate into what you want them to see. Sort of like the technique of pointillism in art... (hell, the quickest way to draw chainmail in an illustration or paint it on a flat surface is to just use alternating black and silver dots.)
For small holes or armor damage, just an uneven black dot or bright silver streak will do to suggest a bullet hole or collision damage. For large holes in armor, once the actual paint scheme is dry, just paint on an uneven black spot with a handful of really tiny silver dots around the edges to represent the ragged shards of bent metal protruding from the hole.
When I was performing with the local
Rocky Horror Picture Show cast, playing Eddie, to represent
the scar on his forehead where they removed his brain solely with makeup, I used to draw it on like this:
Folks would come up to me after the show and be shocked that it was just two-dimensional -- they thought I'd been wearing FX prostetics...