Clem,
Nice idea, but in my experience (and I am in a maintenance window now cleaning all the cars on my layout, about 150) the only way to ensure each wheel is perfectly clean is to put the car upside down in a cradle and clean them one....wheel.....at.....a.....time. Yep, time consuming, but not difficult. IMHO my cars are worth this effort.
I wear a heavy latex glove, spray a bit of goo gone on a rag, spin the wheel set with my non-glove hand and rub away. I do one side of one truck at a time, and remove the dissolved gunk with a clean rag. Really gunked up wheels take a bit longer but the goo gone will dissolve it off. Seventy cars into the project and I figure about 5-6 minutes per car.
I haven't tried denatured alcohol yet but based on my experience cleaning track, if the wheels aren't too dirty denatured alcohol could be substituted for goo gone.
Dave