Wiper blades is composed of synthetic rubber that is designed to swipe across the windshield at a particular angle and not 90 degrees or else, it will not function properly, also it will sqeak. But the thing is, a brand new wiper blade is already designed in such a way like a plug n play hardaware to your pc. No need for other added methods of installation rectifications,etc. like re-aligning, etc.
Here is what's happening to your car...
Its all about FRICTION. You have brand new wiper blade, meaning a very clean rubber in contact with your VERY clean windshield (you said you buffed it quite a lot using Rain x rain repellant). I am not telling you that buffing your windshield with Rain X is bad, in fact it is good. Helps keep your vision clear during rainy days. But the thing is, there should be low coefficient of FRICTION between the rubber blade and the windshield (in fact, the reason why its squeaking is because the HIGH coefficient of friction between the windshield & wiper rubber CAUSES the rubber to GRIP the windshield, much like acting a rubber mat, causing it to move at 90 degrees angle which is not its designed motion), without compromising the clarity if the glass.
How would you do this? Simple.

Try putting/applying lubricant or rubber conditioner along the contact surface of your wiper blade. But dont use oil or petroleum based types. This will surely lubricate and I WILL GUARANTEE you that the squeaking will disappear BUT prepare for the SMUDGES that it will create. Im sure you dont want that . SILICONE lubricants will do this. You can buy at Ace Hardware in SM malls. Just ask the sales there. There is also a lubricant for power windows, I think its also the same components and you may opt also to use that. Basically the same concept of stopping squeaks, instead of the rubber moving, the glass(window) is moving up or down, unlike in a wiper system that the rubber is the one moving. This will solve your problem. and not by any mechanical alterations on your system.

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