fill a bowl with 4 cups of warm water and 1 teaspoon of dish soap, then wipe down both the front and rear grill with a cloth. For dusty corners, I use a small cleaning brush or toothbrush.
The motor housing only gets a barely damp cloth, never a soaking wet one. If dust is packed into vents, I use a vacuum brush attachment or canned air outdoors. This whole extra step adds maybe 10 minutes, but it makes the fan blow cleaner air and look much better when reassembled.
