this is what i did in my garage..
cover all the walls and ceiling with a light thin plastic and make it as tight as possible to eliminate the plastic from blowing with the air movement from the fan, try to have the garage as empty as possible, sweep and blow it out really well the night before. i have the fresh air inlets at the bottom of the front garage door and there are 4 big filters all the way across the bottom, at the back of the garage there is a door leading outside into the back yard. i bought a cheap door from lowes and cut two holes in it and braced it very well and mounted two small attic fans in the doors, when ever i plan on painting, i pull the pins out of the regular door take it off and hang the new door with the fans. i also fabricated a box that goes in front and behind the fans that houses 5 filters to catch the overspray. three filters before the fan and two after. this is pretty extravagent for the one time paintjob, but i paint in my garage on a regular basis and i have never had fumes go into my home and i have never had overspray on any vehicles outside. i also wet the floor and all the filters before i start spraying and again before i start clearing. i have turned out some very nice paintwork in my garage and have never had any complaints from any of my neighbors.