Wheels are just as important as track on cleanliness.
CRC electrical contact cleaner on a rag works very well and contains a surface treatment to stop rust/corrosion. Plastic safe I think. Physically, Ive never seen any damaged and I've emptied dozens of cans at work. But it may discolor "something" slightly; so test your track plastic on the underside so you aren't out for my blood 
(CRC was suggested by OGRF's own Allan Arnold; Thanks. I always had a can, but never thought àbout track)
Weight can improve a connection. Pressure reduces resistance a LOT.
Never "Goof Off"... Goo Gone and Goof Off are often confused. Goof Off is basically Xylene and will take paint off a brick and melt some plastics. Goo Gone is citrus based. Though a good cleaner, I have concerns with citrus products left on metal long term, even if it's citrus oil vs citrus acid. (I don't know for sure, but it just seems kinda risky until I LEARN more) (not to mention I know it creeps into some layered products and causes laminent separation over time)
Alcohol also strips oils from metal. We want a trace of oil to stop rust/corrosion. So say you use naptha, alcohol, etc.. Re-oil railz with a rag and something light like Wahl hair clipper oil, which is more about conditioning metal than lubing. (like cleaning a gun). Wipe dry; enough oil remains there to protect things. It may effect traction slightly for a short while. It should clear up with some laps, but you can wipe again too
Don't forget the allergy pills... sneezes are bad hurricanes in Z scale.
(couldn't help myself... I"ll mod small gauge, but I don't want to run it much. I'm too "Skeered" of hurricanes )
I clean all scales by hand. I might use a car if my layout was huge, but I trust my hands.
