I've done the hanging plastic in the garage thing, and it works ok, but you have to be meticulous about cleaning the garage first, wet the floor down, etc. I've been toying with the idea of making an outside, portable paint booth, using the two support rods from a large dome tent. I thought I would replace the tent material with a heavy duty polyethelene, and cut a hole in one end for a box fan blowing out, and one in the other to duct tape a furnace filter into to provided filtered, cross flow ventilation. The advantage in having it outside would be reduction in the number of lights needed (can't have too much light.) Probably will still need a few spot lights to eliminate shadows.
As far as the comments about personal safety goes, it cannot be stressed enough that you should have your skin completely covered, and use the best mask you can afford. I got a fresh air mask 15 years ago that I still use, and feel that this is one of the best investments I have ever made. Don't take your health for granted!
Matt