Hello! My run has become quite muddy and smelly. I have read about others using sand in their run to neutralize odors and keep the mud away. The run in 4'x8' and I was wondering, how many bags would it take to cover the run? How deep should the sand be? We have considered putting gravel underneath the sand. I also have a 4x4 coop (not a walk-in, though I wish it was!) with a wooden floor. Should I / could I put sand in there too? Any and all advice would be greatly appreciated!! Thanks!