Mewing and Push Swallowing will guide the remaining growth but will not be able to change anything on what has already been done, there is not enough force applied --> You should not hope to change anything.
Excessive Chewing is stupid, is going to bloat your masseter, and if done in an abusive way will shorten your face in a bad way. (But some people want that?)
Bone smashing is pure shit.
Facepulling is probably legit, but only the one you do for several hours a day, with a fairly strong force, and which does not touch the teeth. As a reference the class II elastics manage to push your maxilla back by several mm in a few months, and in general patients do not even wear them seriously, in addition to that, the strength is much less significant than the one that you want to apply with facepulling, so I don't see why an appliance that tries to do the opposite wouldn't work...