To me still air in and area where you cannot filter all of the air is better than moving air. I would be worried about what contaminants you are moving around. A home air conditioner filter does nothing for small stuff and you IMO will be bringing a lot of pollen and small dust into your area. I would focus on making sure I had good air to breath and keeping the air in the room still. Let the dust would settle to the ground and your dry car (tack it off) and not on your wet paint.
Again I am not an expert here so feel free to dispute me!