Knowing nothing more about this than what I have read, I entirely agree with Mary.
Note that when hand propping a Lycoming/Continental powered Cessna, once it's running, you're going to have to cross to the other side of the plane to get in, or access to the controls [to stop it]. For a hand propped Cherokee, it's a long walk around the wing, or a dangerous jump over it. So all being considered, simply restrain it from forward motion effectively while you hand prop it.
Also worth noting that both those planes are Lycoming powered. If a battery start was attempted and failed, there's a good chance that the starter "bendix" is still engaged, which will make hand propping nearly impossible. And, the 172RG at least would be injected, which are not easy to get running by hand propping either. For some older types, hand propping is the way to go. But really, if hand propping was not trained to you during your training on that type, it's a good idea to not attempt it unless you really know a lot about the systems of that aircraft.
But, I have to agree that if it killed him, he did get it running!