It really does get matted up, and does tend to get stuck to the dirt. some people use a coarse sand, as it drains well and keeps claws filed down but the individual feces need to be scooped out of the sand.
Also the coop in my aviary doesn't have water or food in it, especaly at night. once a water dish is on the ground, it becomes more or less a toy. The water dishes in my aviary are on top of milk crates anchored in deep hay, with a safe slab of wood across the middle of the bowl, it discorages...
I used to have mine on dirt, a nice dense layer of hay has worked well, it has to be changed and/or tilled every once in a while to prevent too much molds from growing, the moist, rotted hay is good to spread on top of garden beds.
...My aviary has a good roof on it though. Keeping out the rain...