the glass polish kit is for scratches,,,
![bigthumbup](images/emoji/happy/bigthumbup.gif)
, if the scratches are deep ,, then your wasting your time.,., if there minor scratches the polish will make your windshield look new for months.. and yes it will need to be done again after a few months of rain/washing on the car.. just waxing your car,, it will only last so long before you need to repeat.
the Bon Ami is for hard water stains and acid rain spots, you know the ones that just won't go away when you dry the car off,,,,
so first you would want to get rid of the scratches by doing the polish step,,,, and after the clean up only, you would want to use the Bon Ami if there are water spots that won't rub off when you dry the outside of the windshield off,,,,, more than likely you won't have the water spots on the windshield untill you wash the car later! But the sides of the car will have the spots,, so if no water spots ,, no Bon Ami needed on windshield.
so use it on the sides as well as the windshield
that Bon Ami works real good if you follow the directions.,.