You can also buy disposable icing bags at the supermarket, or make your own from a grease proof paper triangle.
Ok, I just found this video about how to fill an icing bag that makes filling and cleaning SO EASY! Truly mind blowing, if you are at all interested in using piped icing you have to watch it!http://dollarstorecrafts.com/2011/09/mind-blowing-cake-decorating-tip/I feel like whipping a batch of this frosting just to try it.