I've had to shovel coals out to make roof for fresh fuel, kinda wasteful but you gotta do what you gotta do. I think next time I evac coals I might try to seal the pail with aluminum foil to make charcoal, worth a try right.
I've put them in a 5 gal bucket half full of water, let them sit for 2-3 minutes, then spread them out on an old window screen to dry for a week or two. I've made lots and lots of charcoal this way.
Water absorbs a tremendous amount of btus. The water in the bucket gets barely lukewarm.