Ok, I'll start with how I prepare for what Mother Nature might throw at me.
In Northern Ireland it rains on average every other day, so the brolly is pretty much a permanent feature on my bag. In my bag there is a spare towel, a lightweight Galvin Green top which I wear if rain might come but the day has started dry, dry hands which helps in the rain, a all weather glove by mizuno that is good in the wet as well.
I carry special sports bars and drinks made by a company called Science in Sport to keep myself well hydrated and fed during long rounds.
The most important tool in the wind and rain, I find, is to lower my expectations on how I'll play and score.
[Bold emphasis by Yoda.]
Good stuff, GP. What is the "dry hands" you refer to? Is this a special product?