I was told that cleaning compounds leave a residue on the rails that actually attracts dirt and grease, all over again. So the cleaning cars that I use simply have a felt pad that drags along the rails, cleans the railheads and works well for me. If I have paint, glue or stain residue on the railheads, I use a Bright Boy abrasive block to remove the specific problem.
Of course, if you don't clean the track regularly, (about twice a year or so) you can get a build up of grime that transfers over to the wheels and pick-up rollers of your equipment, and you may need to scrape out the wheels, flanges and rollers of each car and engine. Lot of time spent on this project.
Paul Fischer