I have painted my issue M-16 at my last 3 duty stations, but find that after repeated handling, the paint will polish and become shiny, and need more paint. On the last 2, I created my own camo tape that beats just about any on the market. I start with a high quality 50/50 blend in whatever pattern matches my work environment (currently have Sniper, is a good match for eastern woodland). Then I stick Duck brand double sided carpet tape, which is very thin, sticky, and strongly resists peeling, and comes in different widths. Applying it takes a while, as it has to be cut a little at a time, but it is well worth the effort. I find a taped finish softens the outline as well, and really improves grippiness.
I will try to posts pics with different backgrounds and my hand made 3-D camo suit. That's another story.