I use Rain-X on windshield and helmet visor plastic. It works great to get rid of water without having windshield wipers. It works sort of OK on helmet visor. I also have a little "finger windshield wiper" to help with the helmet visor.
Naysayers say Rain-X will turn plastic yellow. I have been using Rain-X for over 20 years, and still have yet to see anything turn yellow. You don't have to put it on every day or month or whatever. It lasts quite a long time. It also makes easy to keep snow (yeah, snow!) off the windshield. Put some on headlight glass for the same effects.
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2014 полынь зеленый гU
Сибирь Экспресс #2