I've seen the tuner lube argument for 20 years... Some people swear by it, some people swear
at it...
I have worked in electronics in some fashion or another for over 20 years and have used tuner lube for everything from large electric motor brushes to carbon traces on $70,000 audio console faders. It is not really designed for faders, but old worn faders get pits in the carbon traces and the "conductive" properties of the tuner lube help smooth out the "pops" that would otherwise require replacing a fader. It also helps protect the fader from further wear until it can be replaced. This is particularly valuable when one is on the road and cannot easily do a major overhaul of the console.
That said, it gives you an idea of how non destructive the stuff is on something like cast metal parts. Anyone who says you will ruin your rails or wheels by using the stuff is full of baloney...
The only drawback that I have found using the stuff on the layout is that it has a slightly greasy texture that does not dry out. This tends to pick up little bits of "crud" from the layout (dust, loose ballast, etc). I just hit the truck with Blue Shower (the industrial version of tuner cleaner) and re-apply the lube. I have tried every idea that has come along (wet rails, dry rails--I even gold plated the tops of the rails back in my jeweler days) and I have yet to find something as easy and reliable as the method you use. If it's good enough for critical components in the electronics industry (communications, aerospace, security, emergency systems), it's good enough for our little models...
Tom F