I haven't read all the posts so perhaps someone has already mentioned this. It makes no sense to attempt to clean the wheels by putting Wahl, or any other cleaner, on the rails. That will take forever as the wheels keep depositing crud on the rails, and it spreads to other wheels. Bite the bullet and clean all wheels, then the track. I have replaced plastic wheels with metal and have noticed wheels stay cleaner longer. To clean wheels, I use a jewelers screwdriver and scrape when the buildup is as bad as you descibe. It doesn't take much pressure and you won't scratch the wheels if done lightly. A buildup of the crud takes a lot of cleaner and towel to clean, scraping is much easier. I have a large fleet also, most of my cars are in a staging yard at any given time, so I run out one train ata time, do each car, return to staging, etc. I do not have formal operating sessions yet so can get by and operate with 25% of my fleet for awhile. So I don't have to do all the cars at one session. I did maybe 3 sessions. Since I did this the first time, maybe 2 years ago, I haven't had to do it again. I don't use any track cleaner or oil. My layout is in the basement and although I took steps to reduce dust, its there. When I haven't run trains in awhile, I run a track cleaning train consisting of masonite pad cars and a Tonys Train Exchange track cleaning car. I run it dry. This removes the dust from the track before it gets back on my wheels. I've never used Wahl, have read its praises. Nonetheless, I would think oil and dust equal crud. Must remove dust!