I have a bad scar on my arm from a burn. I use scar concealing makeup for it that I got from a professional stage makeup store. I think stage performers use this stuff a lot. It was not cheap but it comes in a huge container and will last me at least a year. It works relatively well. It's also waterproof, so I don't have to worry about it coming off when I'm working out.
I do however use loose powder on top of the concealer to set it. It takes away any shine (which makes it apparent that there is a product there) and it makes the concealer last longer.