Some of the things people on here use in nests are wood shavings, hay, straw, shredded paper, carpet, rags, Spanish moss, and feed bags. I cut and dry tall grass from places I don't weed eat or mow, closer to hay than anything else. In my opinion it should be something available and relatively inexpensive. Try something. If you don't like it try something else.
The coop is harder to talk about because each coop is so unique. If it stays dry about anything will work fairy well. If it gets wet and stays wet about anything won't work. You have the poop load portion of the equation. If they spend all day every day outside they don't poop inside as much so poop builds up slower inside. The poop can build up under the roosts because they poop at night and are not moving around to spread that out. You typically have to manage the poop under the roosts. That might be droppings boards or digging it out under the roosts and removing it from the coop. if your coop is big enough you might be OK for a while just tossing corn or something similar on the poop area, they will scatter it scratching for the corn.
Think of the bedding as a diaper. It's job is to absorb moisture from the poop so the poop dries out. As long as the poop dries out you are OK. But if it stays wet it will stink and become unhealthy.
Some people turn their coop floor into a compost pile. That's a bit of a balancing act. For it to compost it needs to stay moist enough so the microbes breaking it down have enough moisture to live and reproduce but not so wet it gets stinky. The ideal moisture level is described as soaking a sponge and wringing it out as much as you can. If you do this you can put anything in it that would go into a compost pile: kitchen wastes, garden waste and excess, grass trimmings, dry leaves, practically anything. You want more browns than greens. Chicken poop is considered a green.
I don't do this. I keep my coop floor so dry that the stuff never breaks down. I use droppings boards to remove excess poop. I spread wood shavings as needed because they get scratched to shreds. I clean this out every three or four years, not because it needs it but I want that stuff on the garden. I should do it more often but I'm lazy. The way some people manage their coops they have to clean them out on a real regular basis, maybe even weekly. There is a big difference in a big walk-in coop and a tiny elevated one. If I were keeping chicken in suburbia I'd probably have a tiny elevated one. It would still be big for the number of chickens I had.
What materials do people use for the coop floor? Dirt, sand, wood shavings, wood chips, hay, straw, and dried leaves tend to be the most popular but really anything that can act as a diaper that they wont eat. Each coop is different and some things work better for some of us than others. Sometimes it takes trial and error to find what's best for you.
Good luck!
the pictures are where I’m building the run off the side of the shed and the coop will be under my workbench.
