All I can recommend is washing in the shade. The water "spots" that are hard to remove are actually etchings from sunlight being magnified by the water droplets. Other water spots are mineral deposits, which usually wipe off easily if you catch them quickly.
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'10 PW 370Z 7AT - wife's car - Project Raspberry Cheesecake
'08 Evo X - built motor+trans | BB-X @ 32 psi | CH3OH | self-built+tuned - ??? WHP
'01 Galant V6 - built motor | GT35R | self-built+tuned - 550+ WHP (retired) |