Gallina--you might want to switch out the nestboxes. The oils in cedar are harmful to the airways of chickens, and would be especially bad if in an enclosed area (such as a nest box). Mixed in on the floor of a coop is probably not so bad, but if you can smell it, get it out. DE will help with...
My dropping board is covered in Stall Dry--you can see a pic of it on this thread:
https://www.backyardchickens.com/forum/viewtopic.php?id=273800
The Stall Dry I use says it is composed of Clay and DE, and it is not dusty (lots of animals on the bag). I NEVER see the chickens peck at it. If you...