Yep, catman, I use that hi-beam flash too -- usually use it for oncoming cars and those stopped at intersections and the horn for those I'm flowing with. Practice that too schuppie!
As far as wet and rain, use the search function on this site and you should find tons of comments.
I'll say this at least: All painted markings on pavement are slippery as heck when wet and will cause an instant lay down if you're not careful! Includes divider lines, intersection markings, symbols, words, etc. Also metal things like manhole covers, railroad tracks (especially if they cross the road at an angle) and some bridges that have metal in them are just as slippery.
You really need a good rain jacket with cinches at the wrists and elastic waist at the very least.
When rain gets more than moderate, most riders will pull off and wait it out cause it's such a pain. It's a good idea, when you are in rain or know you're about to get rained on, to think of places in advance to get off and under some cover, such as anyplace with an awning, covered sidewalks, gas stations, so on.
