I keep those shoe polish rags (the ones the fancy hotels give out to their guests in the room with the soap and shampoo) on my dryer. When dust and detergent accumulates, I run it under the water filling the washer, wipe down the washer and dryer and throw it in with the load I'm washing. After it's dry, it goes back in a basket on top of the dryer ready for the next time the appliances need a good wiping down.