I am no expert with the Callistemon but I do have a couple of observations.
It seems they are quite good at back budding on old wood. But it seems they can also get quite stressed by being cut back very hard.
I found this when a stock tree (given to me by the mother in law I think) that was not much good for anything except that it had an interesting curve at the top. So I decided to cut everything away at this point just leaving a little leader in the hope that this interesting part could be air layered of later.
Over the next week the leaves left at the top started to wither and die. Nothing else had been done to the tree and the lower branches still grew as normal. I have never seen anything like this happen on a tree before. (although there was the weird happening of a gum that was booming in the ground up and cark it after the third heavy prune in one season as it was growing so fast

)
I discussed this with Pup and he stated that they do not like to be cut back too hard (callistemon), although generally they do not seem to have a problem if you cut them back past any leaves as it has been seen with some other natives.
After about a month this top section then decided to sprout out agian which is in itself very wierd and not what you would expect from a normal tree considering that it seemed like the tree had made a serious decision to just give up on this top section.
This lead me to trying to leave as much foliage on collected trees as possible while still considering the balance between root and shoot reduction.
The only conclusion I have come to is that there are many exceptions to the rule with callistemons and many other of our natives.
Keep the experiments coming

It's too bad your in such a hurry cause the stories I could tell you, Bushels and baskets of stories, hole crates full of stories. But if you can spare a moment I will tell you one story.