I tried mixing two large bags of coffee chaff in one coop a couple of weeks ago with the pine shavings. It seemed to work good. The existing shavings in the coop are dirty and need to be replaced. I am going to replace the shavings within the next couple of weeks. When I replace them I am going to mix them half and half with coffee chaff.
Coffee chaff can be acquired free of charge from many local coffee roasters. Look in the phone book for roasters, not coffee shops. The first roaster that I talked to was more than happy to give me as much chaff as I want. They give it away in large very nice burlap bags. I am going to stop by in the next few days in hopes of getting several bags.