I really love Feather-Dri from 3rivers. It comes as a silicon powder. You pour some powder in a ziploc bag, put the fletching end of the arrow in the baggy, and rub it into the feathers. It takes 2-3 shots with each arrow to puff the excess powder off, but once you have them done they last the whole season.
There's even videos out there of guys dipping their fletchings in buckets of water for 5+ minutes and when they pull them out they're good as new. Water just beads off the feathers. I'll probably never use anything else.