For my 16" polished wheels, I washed them just as you would for the rest of the car, but last, and with a seperate rag-as the brake dust often "ruined" the rag.
After that I then dry it and apply wax to the wheel. let that dry and polish it off.
Did that every day last summer, and washed the whole car every other day
Wheels still shinin' strong, and some say the wax helps prevent road debris marks...who knows...
Now that I think of it that is what a friend of mine uses to darken/polish the cladding on his GMC syclone. He applies puts it on with rubber gloves and an old sock, which is now indeed black. There may be additives to it.
that's wheel cleaner, not tire treatment. that stuff is supposed to be a spray-on and rinse-off with no scrubbing inbetween. although the black magic tire stuff does work and work for a long time, it is just a high gloss oil that won't wash off easily. it's not as gunky if you use the applicator to put it on though.
speaking of wheel care... i gotta wax mine next time i wash it. best way i know how is to use soap and water to get the grime off, then dry with a chamois or cloth that you didn't use for your car, then wax it. i've only waxed once, but it sure makes cleaning the wheels a LOT easier. good luck corwin.