Tanky:
The camo question. I just use the paint that is in the brush to fill in the area. I think that 2 thin coats may be better than one thicker coat, but that is just me.
The booth question: I have read and seen some use an old overhead stove/ oven hood to vent out fumes. The ones that recirculate air through a filter then out the sides. Cost of these can vary. Depending on where you get the hood from. I have also read that an old brushless computer fan can be mounted to a homemade booth and vented out an existing dryer duct. That the guy T'd into.
The one I have seen cost the guy about 75-100 dollars, but he built it himself out of plywood and found the stove hood at a used appliance shop.
Good luck with this and hope I gave ya a couple of ideas you can use.
Paul