You use the flushing connection by hooking up a water hose (don't use your clean city water hose!), opening the black water drain, and turning on the flush water. You can close the black drain valve to somewhat fill the black tank, but if you do, be careful. Open the black tank valve before the black tank fills up. You don't want to fill the black tank or you'll have "stuff" coming out where you definitely do NOT want it!
You might want to look at exactly where that flush line enters the black tank. Ideally, it should be directly opposite the tank drain. But I see on my Mini-Lite that it enters the tank just above the drain. Doesn't do much good there, IMHO. For that reason, I have never used it. I may actually buy a new fitting and install another one opposite the drain.
The Camco Tornado actually spins the water; I may get one of these.
I suspect the ones FR installs is simply a hole the water comes out of. I doubt it even really "sprays."