Get a high speed buffer with a wool compounding pad and use a heavy duty rubbing coupound, (I use 3M) to cut fresh paint. It will break down and polish the glass as you go and blend in other spots as well.
Been doing this over 30 years and it also helps on front windshields to clear up scratches from bad wiper blades.
Vehicles were made to be driven! Classic is cool but stock is boring!