Back in 2019 I used a normal garden rooting hormone powder(Doff) which I happened to have in my cupboard. I wetted and made it into a paste then painted it onto the upper edge of the top layering cut. Then secured the split pot to the tree and filled with Akadama mix ,with moss and wrapped the whole layer in kitchen cling- film.I watered occasionally then left it alone.Last Summer here we had record High temperatures which might have inhibited rooting.
Last autumn I checked it and couldnt see any sign of roots.
In May this year when I checked I found a few roots, but the tree had partially callused and bridged over the cut , so I recut it and cleaned up, applied more hormone and re- wrapped it, so most of the new roots have grown since May 2020.