I use a paper towel, or a rag will do, and soak a good part of it in isopropyl alcohol and gently clean the blade area (both sides) that sweep the windscreen. I then clean the windscreen with another towel/rag with the same chemical. Then with window cleaner I clean the windscreen a few times. If that doesn't get it done, change out the wiper blades. At this time of year with winter right around the corner, I change mine out for a new set anyway.