G,day Bohdi, I like the story this tree is telling

also the one you are

. However as all ways there is one, that pot I think is over ambitious.
The same pot with at least double that depth, otherwise you will struggle to keep it alive, unless you do as Grant says, permanent, water tray which then takes away what you want, a nice looking tree in a shallow pot.
When it comes to hollowing out do it slowly so you can see where you are going. Some of the growth is close to the edges might suffer and not survive.
The idea that Mitchell has suggested with the wire brush is what I do. Also a water based paint mix of Fremantle Sail ( from Mitre 10 ) then wire brush gives the old wind blown affect of old burnt wood. also lime sulphur and India or Sumi ink, you can add as you need for lighter or darker.
When using the Blowtorch cover the live foliage with a damp cloth, but also be careful not to spend too much time, at one time near the foliage.
Looking forward to this trees development. Cheers

Pup