My experience with Rain-X on the windshield is...Don't get any R-X on your wipers themselves as it will dry the rubber quickly and make them chatter.
Also, DO NOT clean your wiper blades with those alcohol packets provided with your new wipers...Disgard them ASAP as alcohol dries rubber wiper blades even if it clean them well. Use Ammonia on the wiper blades on a paper towel or just wash the blades(and get off the grit) with your favorite car wash soap while your washing your vehicle
Everybody has their own method...Using Rain-X as directed calls for applying to your windshield, let dry and remove...Wheather you let the R-X dry or just keep rubbing til it drys, it doesn't matter!
Anyway, this drying causes a smearing effect of the R-X which is what I find hard to remove PROPERLY. Then, whatever is remaining on the glass, gets on the wiper blade rubber, causing them to dry and become more brittle and chatter over the glass.
What I do when applying R-X to my glass is:
1st, clean the windshield with your favorite cleaner or car wash soap and dry the glass with the wiper blades in the UP position. Applying product dry on the windshield will cause etching over time. So, use lots of water, soap, cleaner, whatever! Do it WET!
2nd, apply R-X to the(DRIED) glass liberaly and let dry while you do other things to the vehicle such as vacuum clean or tires/wheels.
3rd, only then do I start washing the vehicle cleaning the wheels and tires(with their own sponge/bucket) then moving to the vehicle at the top and working downward.
4th, remove the R-X from the windshield during your normal carwashing, When you dry your car/vehicle, the glass will shine nicely/cleanly while still having the benefits of RAIN-X.
This way, I can remove the R-X without killing myself trying to remove the smearing effect that the R-X leaves on the glass.
You'll still leave enough R-X on the glass to do it's job for that 3-4 weeks or less and not get any R-X on the wiper blades.
This sounds like alot but, it's not! It's just doing the job in a different order.