You can use polish compound to polish the windscreen to become smooth. just like applied rain x. culprit was the harden water stains.

How rain X dispel water is with its silicon compound. Its not really reliable, which is why after sometime cooked under the sun, it will peel off. This causes uneven surface which skips or jutters your wipers. You will need to re apply the compound over and over again, just to cover off the peeled spots.

I would recommend compound such as AGC/22. The ingredient consist of teflon which lasts a very long time. 8-12 months based on my experience after a single application. if the windscreen gets sticky, just use a green scotchbrite to scrub off the harden debris and you will still have the teflon layer exposed. Compound requires a bit of special handling and it will harden under UV. Highly recommended as its certified to be used under aircraft.

yup. else you can buy me milo ais, I bring my very old chemical to apply foc. Hope its not crystallized yet sitting in the store room for so many years.