Hi Brian,

If it's like a film on top of the wheel, a claybar may do the trick, or it sounds like the better option would be to get a light diminishing abrasive such as Poorboys SSR 2. This will abraid the surface slightly but, will polish out to nothing while you work it, thus leaving a nice shiny, white wheel.

You should afterwards put a coat of sealant or wax on the wheels to give them some protection over the winter.

Hope that helps. Give me a shout if you need any info on products.

Cheers.
Alex.