I made a quick and simple track cleaner for my new RR. During our train show last Christmas, I bought a Bachman circus train with a Porter engine flatcar and Emmit Kelly caboose. I plan to bash the cars (the locy I already repainted).
I discovered if I took a sanding sponge I had and trimmed it to length, it would pressure fit perfectly between the lower truss supports on the caboose. I added a wedge shaped shim between the sponge and the body to make contact with the rails and canted it slightly to lift the bow edge above the rail joints to prevent it from catching.
After a few laps around the track, a pencil mark I made on the top of a rail was cleaned off. I can easily flip the sponge end for end or upside down as needed.
FWIW.