check this out-I found it very helpful when I first decided to switch to sand as litter in my coop.
http://www.the-chicken-chick.com/chicken-coop-bedding-sand-litter/
I use dry contractors sand from Home Depot-play sand is usually wet--i learned the hard way it gets stinky fast! keep sand dry, scoop the poops and its great in the run!
the sand grains should be different sizes.