First thing I do is litter train them. This alone elimates alot of the smell. Litter training is easy enough. I just put 2 or 3 poops from each rattie in the litter pan (uncovered) and they seem to catch on fairly quickly. I also buy a very fine litter with baking soda in it. Next I line my hammocks with old materials. (This was my husbands idea and it works great) I cut up all clothes that are worn out or out grown, and toss them in. Ratties love it! They chew, re-arrange, walk in and out of, make pillows for their little heads and in the cold weather, they cover them selves like there blankets. When stinky, I toss them out. No washing, no stink. You can also leave the hammocks in longer, cause the pee soaks into the clothing. I cut up everythink soft, even old socks! (By the way, socks are great after surgery. Cut 3 little holes in the toe area and you have an instant dress. Sometimes hard for walking, but they do the trick for the first couple days when healing is most important. I find you have to pick out "wandering poo's" every day. Not an easy fix, but every little thing helps.