I don't have that many (suburban) chickens so when I built a coop I included 3 nest boxes. But the gals seem to always make a 4th next box so I "let" them claim this preferred box to avoid what I call "Nest Box Wars".
I cleaned out my 4 boxes to kick off the semi-annual deep litter cleaning of the coop which this year will include painting and minor repairs. I like to do this when the weather is still warm enough for the coop to dry out because I hose the whole thing off.
I start with the next boxes in hopes that they dry fast enough for the ladies to have access fairly quickly. And I will let them free range to distract them from the coop takeover and spraying out. I will power hose everything, scrape anything that is still sticking, then scrub & mop up the remaining. My coop (It's really more like a pampered chicken hotel) is off the ground and when I built it, I tiled the floor layer because I had some tiles laying around. It does make it easier to clean. The nest boxes themselves are just wood (except for the bonus next box which is on the "tiled floor" of the coop and is marked off by a stack of bricks for privacy.
When I dump out the contents of the coop, it goes to the dirt ground 3' below the coop. This composts further until I use it in my garden.
When I put new shavings in the boxes, I always put
diatomaceous earth in under the shavings. Sometimes I add some dried garden herbs. This time, I happened to go to the thrift store and saw an unopened pack of excelsior nesting pads. I tried one and it lasted pretty well (middle dirty picture) so I tried 2 more this time, in boxes 2 and 3. I like them because they cover the slight hole in the board that leaks shavings down below in my setup.
Meanwhile, the other 2 boxes got regular pine shavings. Box 1 is too narrow and the bonus box is level with the pine shavings on the floor of the coop so it makes sense.
Viola! clean boxes.