97-SC300

iTrader: (17)

Another option (very commonly used by many pro detailers) is to clay the exterior windows and use a paint sealant on them. Any paint sealant will work and it's extremely effective. One coat will last you several months easy. My favorite sealant is the BFWD that's sold by the forum sponsor ProperAutoCare.

Artsplace

I have put a couple of drops of rain x in my show car detailer spray and it works extremely well!

Todd@ProperAutoCare

+1. While I have found that Glass Science works marginally better than a sealant, Wet Diamond works extremely well and is SO easy to use.

In my non-scientific test (I applied Glass Science to half of the windshield and a paint sealant to the other half) I noticed that water will begin to bead and sheet off at about a 5 mph lower speed. Also I seemed to get about an extra month of durability. However, if you are sealing your glass every time you seal your car it should make too much of a difference.