i dont think diverting the aggression to another object is a good way to deal with hitting as your still saying its ok to hit/punch. IMO it isnt at all.
when dd was doing it i would hold her hands and run them over my face (usually where she hit me) while saying "this is what we do to mummys face.....gentle"
i think you want to encourage the gentle behaviour not the rough/aggressive/violent behavior
That's what I do with DD. It stops her from doing it in the moment, I'm hoping she'll realize that's what I want from her all the time soon!