From what I have heard this is a way to do it. Put on box fan in the window blowing out and have to box fans in under the big garage door blowing in. Make sure the 2 fans have plastic around them to cover the open space under the door. If you have more air flow coming in then going out, that makes sure that the dust and dirt from and cracks, spaces etc. do not get sucked onto your paint. Hopefully I explained it the right way. I myself have not done this but have read about it so take what I say and use your own judgment if it makes sense to you. Ooh, make sure you have filters attached to the fans.