How can you remove windshield rain repellent residue?

You can remove almost anything from a window using a fine mesh steel wool as long as you use it on glass (not plexiglass or window tint) or even chrome. It will not scratch glass or chrome. This is what body shops use to get any overspray from paint off of windshields. I've even used it to get concrete off of chrome wheels, so rain repellent shouldn't put up too much of a fight. If it does, you can always use soap water with steel wool to help get it off. Just be careful to not scratch paint or leave any wool shavings on paint so you don't pick it up with a sponge next time you wash your car and end up with scratched paint.