I bought the windshield stripping paste in the windshield wiper section at Pep Boys (an auto specialty store). It comes in a tube like tooth paste and is marketed under the name "Wiper Mates". This same company also makes a "pen" that renews the graphite on your wiper. This particular product works ok but doesn't last very long.
Bon-Ami is a general purpose kitchen cleaner that can be found in any grocery store. You will find it in the same section as Comet, Ajax, etc. Bon-Ami is a very old product that your grandmother used to use.
Once you remove the film on your windshield by using one of these products, you won't have to resort to such drastic cleaning efforts for a long time ( unless you wax your windshield at an automated car wash ).