sometimes dirt is a little harder to get off then a damp will allow so i use soft toothbrush as well. i find that brushing down alone isn't much more effective then the damp wash cloth so i will also scrub up in an up and down quick motion. however, be careful while you do this and pay attention to what you're rat is telling you. if you've never brushed your rat's tail before hold thier tail and just brush down, so long as he isn't squeaking when you brush your fine and it will give you a base line reaction for when you need to go up and down. if they act more figgety or squeak when you brush up then you're brushing too hard. and remember too that it COULD be freckles as falconstorm said. some rats do have them.