We are going to cover the ground of their run with a truckload of sand... question is, they have 2 kinds... fine beach sand and coarser screened sand. I would think (just me guessing) that fine sand would be good for dust baths, and coarser sand would be good because they can use it as grit. Can they take dust baths in the coarser sand?? If so, that would be dual purpose. So what do I get???