My old house had a swamp cooler, which cooled the attached garage down quite well, if I left the big door open a few inches. I did not have any more rust issues then here, with nothing to cool the shop. The big difference I notice, is the shop here gets tons of dust form the surrounding desert. The swamp cooler makes a great whole house filter. Our house has central air, which is as good the other house with the swamp cooler, just tons of dust if we have the windows open, and not great cooling when we close the house up.
A neighbor has a swamp cooler on his shop, mostly does wood. His paint booth is slick, he hes three dryer vents, that go outside, and has a lever to force them closed. When he paints, he opens them, closes the windows, and turns the fan on the swamp cooler up. The filtered air, grabs the fumes, and flows out the vents.