I do like adeeden If they are just wet but I also strike my palm with the shaft briskly while steaming.
Sort of steam, then strike a couple of times, then steam and then strike again. The impact seems to get the feathers back to their original position more easily. When I am almost finished, I wave the fletching quickly back and forth, fast enough to make a swishing sound. It works for me.
When they have animal fat and/or blood or other sticky dirt that doesn't just rinse off, I do like Dave.