One thing is to try and negatively pressurize the space if you can, have a fan blowing out, NOT a box fan, those have been known to cause explosions with paint fumes. 


Do a search for homemade paint booths, Its fairly split between positive and negative pressure, but negative will be easier for you to do as Im assuming you wont have a top for your booth, put a fan at the bottom and back fo your booth if possible, then work from top to bottom, front to back. That way you paint over any overspray


Heres one I found you dont have to get too elaborate, as the paint usually wasnt that great from the factory, some mess ups are more factory correct than a 100% perfect paint job.         http://www.homemadetools.net/homemade-negative-pressure-paint-booth