While all those are fine, I have settled on a briteboy and elbow grease as the cheeapest and surest way to clean dirty track, and running your trains everyday to keep it clean. Gives you an excuse to run them everyday. FRED
Welcome to the Gauge...on our club layout, if you look closely, you'd see---gasp---brass rails mixed in with the nickel-silver. As long as its kept clean and well soldered, you shouldn't have a problem.
Thanks! briteboy and wet/dry paper (I have that around for old car stuff) should handle the remedial work. Then on to the maintenance suggestions. And shaygetz, I'm also impure and have mixed brass and nickel. Oh dear.
The HO layout I'm building now uses all recycled track. Besides cleaning the track check to be sure its not bent.
The used turnouts I used had electrical problems so I ground away the ties in spots to solder jumper wires to eliminate the dead spots and future continuity problems.
I would avoid using sandpaprer as it leaves scratches to hold dirt. You want the rails slick and shiney as possible. If the brass is tarnished liquid brass cleaner on a rag works fantastic and will only brighten the tops of the rails if used correctly. FRED