I had so much trouble with powder coat lately that I thought to try and remove moisture from the powder itself.
A couple of years ago I picked up a little Electric Laboratory Dryer. It has a very fine heat adjustment from about 120°F to about 170°F with slight air movement.
I put some powder paint in it that I suspected had gotten contaminated with moisture by being exposed to high humidity long enough to absorb it. (I noticed several years ago when powder coating in the unheated garage at -20F that the powder had big chunks frozen together from the moisture in it.)
After drying some in the lab dryer it seemed to improve the coating ability. So I have since gotten taken apart an old air filter to use the paper as a holder for powder paint so I can run more through the dryer. We will see how that works.