Or you could use a whisker biscuit and not worry about wet feathers!
Seriously. I had some blowhard at an outdoor 3d range one time telling me (after he seen my wb) that a "guy he knew" was hunting with one in the rain and when he took his shot (at a deer) his arrow barely went 10ft.
So being the skeptic that I am , I walked down to the creek , inserted my arrow into creek (fletching end of course) , took some water in my hand and saturated the biscuit , and walked back to where this guy and my buddies were standing at the 20yd stakes. I then proceeded to shoot the soggy arrow (and biscuit) into the 12 ring. The guy then said "his buddy must have been full of s***" and walked away. My buddies said it was the coolest thing they ever seen. When I shot , there was a cloud of mist from the fletchings passing thru the biscuit. Somebody (that shoots a wb) and owns a digital camera should try this and get a pic.