Take a Q tip and use a little dish washing detergent. First wet the Q tip with water. Clean the windshield and then go over it with another Q tip and clean water. Repeat with more clean water and then dry with a clean Q tip. That is how I clean the canopy and windshields on my aircraft models and it should work with car windows.
Berny
Berny
Phormer Phantom Phixer 
On the bench
TF-102A Delta Dagger, 32nd FIS, 54-1370, 1/48 scale. Monogram Pro Modeler with C&H conversion.
Revell F-4E Phantom II 33rd TFW, 58th TFS, 69-260, 1/32 scale.
Tamiya F-4D Phantom II, 13th TFS, 66-8711, 1/32 scale. F-4 Phantom Group Build.