They work…..to a point. Still, “elbow grease” with a light abrasive like a Scotch Brite pad is works the best. However, the cleaner cars do work. They are great for “hard to reach” areas.
I have 3 kinds that I run in a train……
1. the roller car from Cemterline
2. two pad cars from NorthEast trains
3. a rotating disc abrasive car from MNP.
Peter