It works great as long as you do complete coverage of the area. We usually apply it early each spring. It is granular, and we apply it with a rotary spreader.
I think we bought it at Lowes. I think you can get it at most lawn care departments of Walmart, Kmart, Home Depot, etc. You might not find as much until spring. All the "lawn/garden" areas of most stores now are full of Christmas stuff. :P