Expensive but really amazing stuff, the Shimazaki Dry Shake Spray is great for drying and keeping your dry flies floating like a cork all day long. Treat your fly with a quick spray before your first cast.  If your dry fly eventually begins to sink, just give it another quick spray. The absorbing powder in the bottle removes the moisture from the fly and coats it with a water resistant material. Your fly will again float like new.  Very impressive!  Highly recommended for large deer hair flies like deer hair bass poppers and mouse patterns but works well down to tiny dry flies as well.