... use a good rim cleaner, scrub them good using a soft long-bristled brush to get between all the spokes.
Power-spray all the residue off.
Allow rims to completely dry.
Wax the rims a good 2-3 times (they are painted and clear coated from the factory, if you haven't noticed.)
For most of, or the rest of winter, you will be able to pressure-wash them clean with just water alone.
* Keep in mind, if you use rim cleaner after they have been waxed, you will also strip the wax off.