Dave: I just purchased a set of Dust Monkeys and attached one to a car and left run. Running on track that was cleaned several weeks left some black marks on the Monkey.
I will add several more to cars and I believe they will work great and will keep the dust and grim from forming to the point it affects electrical conductivity.
I'll continue to use my A Line Masonite under car pads for cleaning and use them with the Monkeys.
Not sure that my Center Line roller track cleaning cars with dry pads wouldn't do the same work as the Monkeys, but then they are track cleaning cars and the Dust Monkeys are almost invisible when installed and can run in a train undetected.
Will recommend the Dust Monkeys.
Greg