for water spots, try in a couple small locations using undilutted white vinegar. I have occasionally gotten water spots onthe paint and windows, especially if I have to wash my stang on a hot day and it air dries before I can wipe it down.
I use vinegar on water spots on my windows all the time and I have used it on stubborn water marks on my paint and it clears them right up.
1. make sure the car is cool and better yet do it in the shade or in your garage
2. poor a little vinegar on a clean towel and lightly wipe the area with the spots
3. quickly wipe the area with vinegar up with another clean slightly moistened towel.
4. check your work, if cool you will want to apply a quick shot of mequires or mothers, turtle wax premium quick detailer and wipe dry.
this has always worked for me.