When I do my builds I sort my rocks into groups. I go over all of them so I know what I have so I can see shape and size of them. I sort them into base rocks that go under the structure, flat rocks that are used for over hangs and caves, face rocks that are on top of my structure that have a cool shape (prime rock), and ones I call finishing rocks. Those are used to even out UN-natural looking areas or in places like the sand bed to round out an area or added visual affect. When I am about to start my structure I lay the rocks I am going to use out first for easy access and I can easily look at what I have so I can grab the rock that best fits my needs. The face stone I bring out later. I keep a spray bottle filled with tank water and spray them every hr or so. Or if the rock looks like it is drying. If I take a break I spray them and cover in garbage bags.