Don't know about Boeings, but new Airbii come from Toulouse with a tank filled with rain repellant. Tried it once or twice in heavy (in European terms) rain and it seems to work.
Don't know the brand name of this stuff and once is used, the operator never refills it...
My only experience with tropical rains was in ATR. The windshields were supposedly covered with a hydrophobic coating (they did it every year prior to the start of monsoon season, so it was fresh). However, it didn't seem to make any difference. Landing in a good downpour, it felt like looking through a bottom of a bottle. Lots of water on the windshield and everything was distorted. After one or two landings like this, I just preferred to hold and wait till the rain was over...