I made a similar flusher just from material bought at the hardware store. Another thing a person can do to help flush out the water heater, is to open the inlet valve to the heater and let the water run out the rod hole. I'll sometimes plug the hole until the heater is about half full and then unplug the hole. This will give you a little better flushing action.
Roger & Cheryl Full Time since 2002, RVing since 1975 2008 Chevy 3500 Crew Cab Dually, 2012 RW 36RL