Kadee makes a wheel cleaner brush for Largescale engines. It has some wire leads with aligator clips to temporartily attach to track power. The brass brush area is really two separate electrically isolated pads, one pad to each set of wheels.
Touch the pad to the wheels and it will apply power to start the engine running and the brushes will clean off the black stuff.
This is the same principal the other smaller scales have used for years.
Edited by: Dennis Cherry