jfenwick thats a really good idea using poly to make your own makeshift paint booth.
That's an old makeshift booth I did up real quick with some left over poly. Once I had some time I used some 2x2's to make a general frame for it that can be easily disassembled (1.5 car garage is subdivision) and covered that with poly. This way when winter hits I can pull it apart and hang it in the rafters so my wife can park the car in the garage. Installed an explosion proof light and a couple of those square fans with furnace filters....isn't the greatest setup but is enough to do a case at a time. For a while I was planning on using some insulation to try and turn it into an all season booth by adding an electric heater (what explosion hazard?) but just never had the time.
I like the military look as well, I'm relatively new to painting myself, have only been doing it for a few years and have never done anything military themed. Your best bet would be to get some cheap spray paints at walmart or something, get some scrap materials and practice a couple of techniques to make sure you get the look you are going for. Would suck to screw up the HAF.
Wet sanding isn't necessary, I've only ever done it POST painting as part of either the buffing process to get an ultra gloss look or to take out a run or imperfection. And even 800 grit is pretty fine for a prep job, I'd go much lower, medium grit will work fine.