I asked a similar question here a couple of months ago, and several helpful members suggested I clay also. I had a problem with the wiper blades hopping and making squeaking noises and also leaving black residue on the glass.
I scrubbed the blades as suggested, and then used some protectant on them, and clayed the glass. Now I also use EO 20/20. The windshield beads like there is Rain-X on it, and when I have to use the wipers (which is quite often here in Vancouver), they are smooth, quiet, and streak free.
Autopia is the best!:up