Putting them up on the roost @night when it's dark might help. I had 2 pullets last year that stayed under the roosts and they get all poopy from the ones on top. Since I didn't finish their coop roosts until they are 14 wks old. I placed them up on the roost for few consecutive nights (totally dark) except my muted flashlight in my pocket to see where am going. After few nights they got the hang of it. All my hens roosts on their own including the add ons this year.