I bought an appliance from a model shop which does this job. It has two crocodile clips which you attach to the track. Then there is brush attachment which is separated in the middle and has brass wires which cleans the dirt off the wheels. I don't tend to use it too often as it tends to give out electric shocks.It does have a thing which it supposed to earth through but it obviously doesn't work very well.I wouldn't recomend this at all. I generally tend to use a foam block with a light sand paper and carefully remove it with that. I don't knowe if I should recomend this though.