You might try the deep litter method, there are folks that swear by it. For an outside run, some folks throw large, fibrous weeds, twigs from the yard, leaves, garden plants, etc. The moisture stays beneath this mat, the chickens get some good entertainment from scratching for bugs that hide in the litter and it takes a long time to mat down. When it does, they add more. There are experts that say the deep litter method in a coop can provide 100% of the protein needs for chickens. I haven't tried it but I'm thinking about it in one part of my coop area.