Most of the waterproofing things work pretty good........when i shoot feathers i use a product called " Water Shed" intended for Dry Flies when flyfishing. Its a permanent waterproofer and you must apply it at least 24 hours before you use.

By using that and a ' Cat Quiver' I don' t sweat dry feathers when hunting.
The Cat quiver will keep your fetahers bone dry as they are hidden inside of a plastic hood.