CRC Eelectrical cleaner. (Home Depot) Spray on a rag and wipe down track & switches.
Tried that crap (my opinion), and it quickly destroyed the DCS "signal" on our layout! Thus, nothing but denatured alcohol on a cotton rag, wrapped around a short piece of 1X2 inch pine.
H.W., unless others chime in and confirm that CRC destroys DCS signals, I find this a little hard to swallow. I think your theory is full of untreated hot water.
To all others, for a good, deep cleaning, I generally use mineral spirits on a paper towel to clean my tracks (MTH Real Trax). Doesn't seem to take long at all for the towel to turn black. Probably due to a combination of oil, grease, and oxides on the nickel-silver rails. I typically go through 3 or 4 towels when cleaning my basic double-oval 6' x 16' layout. Then, I may go over the tracks with a stiff nylon brush to knock any dry dirt crumbs loose, and finish up with a good vacuuming.
I also have a home-made rail cleaning car utilizing Scotch-Brite types of cleaning pads that I occasionally run over the layout for some light duty maintenance every now and then.
Different track systems undoubtedly will need different cleaning methods. For instance, I WOULDN'T use my current deep cleaning regimen if my layout consisted of GarGraves/Ross track with ballast and painted rails. I'd forgo the nylon brushing, and only vacuum if the ballast was extremely well secured with ballast glue.