I'm not one for modifying bricks. I don't think I'd be that good at it. The same with painting bricks. But there are those in the community that do. MittenNinja did a post on painting Lego here.
Now there's a new one. Courtesy of Brothers Brick. It's really interesting, but there is a bit of crap you have to sit through before it gets to the meat of the matter.
Do with this information what you will.