One idea that I came across several years ago was graphite. The suggestion was to purchase a stick of 4B pure graphite from an art supply store, such as Michael's. A graphite "lead" pencil is no good because the graphite in such pencils has been combined with a type of clay to reduce breakage when sharpened to a pencil point. The article said to use the graphite sparingly, just in a few places around the layout, and all of your track cleaning problems will be solved. I tried this and it worked - perfectly. There was no problem with traction degrading because the amount of graphite used is extremely small.
One of my favourite model railroad authors is Joe Fugate, publisher of the excellent digital publication called Model Railroad Hobbyist Magazine. Joe has written several articles about track cleaning. Recently I was listening to a video by Joe on Trainmaster's TV which is an excellent service I subscribe to. Joe's explanation made so much sense that I now understand why graphite is so effective.
Joe Fugate pointed out that the grime that accumulates on the model railroad track is mainly caused by what he calls "micro-arcing". Below is a picture of a railroad wheel on a rail. On a model railroad, it is this wheel-to-rail contact that completes the electrical circuit to both sides of the locomotive motor as well as any other electrics and electronics that are on board. As a wheel rotates along the rail there are minute sparks or "arcs" that occur at the point of contact (see the yellow star below).
These arcs are much too small to see with the naked eye, even in a darkened room but they are there. Similarly, if you complete an electrical circuit by touching two conductors to the ends of an AA battery there is a minute arc which again is not visible to the naked eye but it is there. Repeated micro arcs between the wheels and rails deposit a layer of metal oxide on the rails and wheels.
Joe's presentation went on to point out that the commutators on virtually all motors (aside from brushless motors of course) are made of graphite because this creates very little arcing compared with metal-to-metal contact. Even the arcing that does occur between the graphite motor brushes and the armature does not create a metal oxide because it is not a metal-to-metal arc.
The advice given in the presentation was to take the above-noted 4B stick of graphite and rub it very gently along the inner corner of the rails. This location helps keep the graphite off the railhead which reduces any potential traction issues, combined with the fact that it must be applied very sparingly - so sparingly that it is not visible. Here is a picture of how to apply:
After listing to Joe Fugate's presentation I now understand why I have had so much success with my track from using graphite. If you don't read Model Railroad Hobbyist or subscribe to Trainmasters TV I recommend you give these a try.