Glass cleaner may get some of the softer, easier water spots off the windows but not the harder spots. At the very least, the glass cleaner removes other dirt and debris from the car so you can easily see the hard spots better. Apply the cleaner from its spray bottle to the entire surface and then wipe it away using clean cloth towels. Use glass cleaner without ammonia; this means you should avoid most household cleaners. You can use basic soap and water in place of glass cleaner for the car body.
Rubbing alcohol can get water spots off if you apply it and clean the car immediately after the rain. It works best if you mix it with water and vinegar, making sure the solution is at least 70 percent alcohol. Apply the alcohol to the rag first and then rub the rag across the surface. Use a very soft cloth and don't rub the surface too hard as you may cause abrasions. Alcohol dries and evaporates quickly, so let the car dry in the shade.
A number of commercial rubbing compounds are designed to remove the spots completely; some even advertise as keeping them away afterward. Many of these compounds require a special brush-like applicator that rubs the compound onto the car. You then must rinse the car off to remove the compound. You may need to do this process multiple times to completely remove all the water stains.
While brush-like applicators are usually recommended for applying rubbing compound, an orbital buffer can be effective. This works especially well because it can apply the compound to the surface quickly before it dries, which is a concern as that can scratch the windows. Use a buffer with a terry cloth bonnet since it is the one of the softest available. Only use the buffer on glass surfaces; using it on the car body can singe your paint job
Recommended Auto Glass Cleaner:
Sprayway Glass Cleaner
Stoner 92166 Invisible Glass
No Touch GS8 Auto Glass StripperAutomotive Glass Cleaners)