I go to Walmart/Home depot and find the cheapest flat spray paints I can find. All flat paints--no matter how fancy they are--achieve flatness by having reduced film binders (which give them strength) and solvents/inert substances which break up the surface--that's what makes a paint look flat by refracting light. I then put two coats of spray satin polyurathane over the spray paint to provide the film hardener--not quite flat but no more glossy than the stock mossy oak cammo jobs I see on the production rifles. I don't mess with the barrel--that would require some fancy work to get a really durable binding finish and I just cammo wrap it if I'm going out in the woods. I'm a artist/painter so I'm not afraid to get creative--the world of cammo effects goes way beyond just spray paint.