Sand doesn't evaporate much moisture from the top. It drains down through the grains.
That means the most important part of using sand is considering what it will be sitting on.
If the surface is solid or has poor drainage, then the wet sand must be dumped, or it will stay wet perpetually.
Poop doesn't have enough moisture for the problem you are describing.
However, any bedding is going to have problems in an under-ventilated coop. With organic matter there would likely be mold instead. So, I would address the ventilation first.
The driest bedding you can get is those pine pellets.
That means the most important part of using sand is considering what it will be sitting on.
If the surface is solid or has poor drainage, then the wet sand must be dumped, or it will stay wet perpetually.
Poop doesn't have enough moisture for the problem you are describing.
However, any bedding is going to have problems in an under-ventilated coop. With organic matter there would likely be mold instead. So, I would address the ventilation first.
The driest bedding you can get is those pine pellets.