billsbowtie
I am not sure about the paint but the best glass cleaner on the market is Bon-Ami
Here is a link from a BMW message board that has some good reading.
Bon-Ami FAQ's
It is great for removing Rain X and a lot of the road rash from you windshield. It takes some elbow grease but worth it. It will also make you wipers slide better if they are in decent condition.