HI all again,
I earn my hobby money doing HVAC. I'm enjoying this thread. Here's another $.02 worth. I metioned adding 3M 77 on a filter in front of a 20" box fan. Use the cheap 30 day filters for this. Pleated filters (clothe looking) would work great by itself. There is also a washable filter that resembles plastic strand matted together. These are also considered permanent filters, and you can cut to size. Think they measure about 24" X 30". These you just taked outside and wash with a mild cleaner and the hose.
Also if you vent outside, you need to have a very drafty house / room, or an intake from where you are exhausting to. Can only remove very little air without replacing it. If you vent outside, you need to replenish that air that your trying to get rid of. Like trying to blow up a wooden ballon, but opposite. Can only pull so much of a vacuum in a wooden room.
If you paint in front of a fan be aware that the motor in that fan should be rated explosion proof. Just a word of caution. I'm guilty of painting in front of a attic fan mounted in a window with a filter in front of it. So take your chanes.
Thats enough from me.