Chemical Guys makes a heavy duty water spot remover - I've never tried it. Ascetic acid / vinegar works. Chrome polish.
As for prevention, I'd go some sort of sealant - most anything'll work. Jescar Powerlock, two layers should give long term protection. Ditto one of the SiO2 sealants. Spritz these onto the wheel then blast it with a heavy water stream. The SiO2 category of products are extremely easy to use. Meguiar's Hybrid Ceramic Wax is an example of the SiO2 family of products and you can use it on wheels, paint, glass, trim, cars, refrigerators, skis, your little sister, anything.
FK1000p would be a winner too.