Usually its better to spend more money on spray paint, as you get what you pay for... thats what ive learned in my years of modeling though...
What color do you want it to be? are you trying to make it a better tan color? or do you want to camo it? Theres a few techniques you can use, however if you dont want to camo it, i wouldnt tell you to use those techniques....
I would suggest either the Krylon camo colors, or Model Master/Testors model paints (as you can get a HUGE variety of military colors and shades from multiple eras and countries)...
Make sure you coat everything atleast once or twice (base coat, and any striping/camoing). Also it would be a good idea to pick up a can or two of Dull Cote (not clear, or gloss) and cover the whole gun once your finished. This will keep your paint on there longer and make it hold up through wear and tear more so than if you just left the paint bare...
As for mags, the below options are fine. pmags would probably look best in a scar. King arms, sarms, and MAG all make good mid cap mags too, im not entirely sure which companies make their mags in tan though, some might only be in the regular gunmetal color.
