I use WD40 Contact Cleaner.
That is great stuff. I use it too but not on my railroad tracks. It's not because it doesn't work. I save it for when I need the spray power to get into small areas. It is mostly non-polar, but it does have a small amount of Isopropyl Alcohol. Which makes it a versatile cleaner and helps it to evaporate quickly.
To be honest the whole polar, non-polar debate is overblown, in my opinion.
Non-polar solvents work great at dissolving non-polar substances, like oils and greases, which I believe are often the culprits behind most residue buildup on track surfaces and rollers. But Isopropyl Alcohol works well for small amounts of oil and grease as well. Using polar cleaners like Isopropyl Alcohol just means you must clean the track more often. Again, this is just my opinion.
I first clean my tracks with (91%) Isopropyl Alcohol. Next, I wipe it with a clean dry cloth. If there is any residue "black gunk" on the cloth I repeat the cleaning with the (91%) Isopropyl Alcohol. Then I treat it with one of the three (mostly non-polar) conductivity enhancers I posted. It works for me. My Lionel Christmas layouts run trouble free for 6-8 weeks or more after being cleaned.
I know people use all kinds of stuff. From Automatic transmission fluid to Naphtha and everything in between. There is always someone recommending something or another. I have stockpiled (91%) Isopropyl Alcohol and the three conductivity enhancers. I'll use what I have until it's gone.
When it comes to micro arching, I have no clue. I do know arching can contribute to the buildup of carbon or “black gunk” on wheels and contacts. With the lights off I would expect to see it, but I seldom have. When I did see it, it was due to a bad connection at a track joint. It could be different with sensitive DCC of which I have little knowledge. I don't see it as a factor with my AC Lionel trains. Legacy, Lionchief or conventional.
I suspect most of the “black gunk” I wipe off my rails is a buildup of oil and or grease from my locomotives and rolling stock.
Bottom line: whatever works.
Yeah I probably need to clean the track.
I think that is all you need to do and WD-40's contact cleaner will certainly do the job.
Keep up the excellent work!