When using this icing to decorate cookies, I generally add a few extra tablespoons of water so that it doesn't end up quite so stiff... I find that I don't generally need this frosting as stiff as this basic recipe makes it. I probably add about ¼ cup additional water (or lemon juice). I base how much water I add on how it looks. You want the icing to be stiff enough so that when you pipe details it will hold it's shape, but not so stiff that you can't get the icing out of the bottles/piping bags easily.
