Did you not use the community search tool (the little magnifying-glass button’ to search for the past threads on ‘track gleaming’? There have been quite a few.
Most current nickel-silver track has ‘drawn’ rails: they are not rolled, but pulled through dies to form the profile. This generally results in a ‘railhead’ with longitudinal scoring and sharp, unprototypical corners. When you attempt to pass electric current between this and the wheels, you often get intermittent contact, and the high inductance of typical DC motors can produce small, but very hot arcing, which we call ‘microarcing’.
The first real step in ‘gleaming’ is to dress the railhead so it is closer to “real” profile, especially in the gauge corner from the contact patch down to flange contact. In particular this step removes any square or sharp inside corner, and any draw marks or other surface issues in contact areas. Note that this involves some substantial stock removal, so you would use fairly coarse abrasive in a form suited for rapid, controllable stock removal.
This is a form of metal polishing, and you should not be surprised to find that the surface finish after this step is not very suitable either for operation or for staying clean – no better than if you were to scrub along with a Bright Boy or similar scrubber to ‘clean the railheads’. You consequently go through the steps involved in actual metal polishing – progressive “sanding”, stoning, or lapping through progressively finer grits until ALL trace of previous coarser scratches have disappeared. (Any remaining scratch profiles will cause contact roughness and serve as a trap for schmutz; a multiple whammy…)
Since this isn’t French or black-polishing for appearance, you can skip some of the usual intermediate grits if you want. Some of our threads have recommended only a few grits, and carrying the formal sanding only down to ~1200 grit, but I’d recommend finer even if the burnishing step will nominally close any slight open scratches. But be VERY CAREFUL to clean all the traces of a pervious grit off before you go to the next finer.
The burnishing is a mechanical process to level any fine remaining scratches or asperities. Most of the ‘washer trick’ methods do this dry, which makes me a bit nervous about introducing new scoring or longitudinal scratches ‘right at the end’ (vs. going up through 12000 grit with lapping film and a 'scope to confirm profile and finish, which is overkill for most hobbyists…) The ‘burnishing liquid’ is a friction modifier that keep the burnisher from finely abrading the surface. You will probably want to remove the traces of burnishing liquid from the surface afterward, for best electrical contact, and this may be difficult because most of those products are formulated for pretty polishing, not contact integrity or surface cleanness.
My advice is not to apply any sort of cleaning product or TOR (top-of-rail) dressing like De-Ox-It or its closely named relatives, or Wahl clipper oil) until all the little microarcing pits and scrapes and scratches have been machined away, and the surface burnished down. At that point it should be relatively easy to dissolve any deposits that form on the rail, and then positively remove the dissolved material with an absorbent wicking pad or John-Allen-style weighted Masonite pad furry-side-down.
Others here will have their own wisdom to add here.