Here's an answer to the rooting hormone question:
ippswr.org/home/ippsna/2005/Presentations/Criley.pdf (see page 10)

I have no personal experience with this plant, but it looked like (with a brief Google check) that there is a reasonable amount of info out there. I didn't see anything related to using a cloner. Maybe you should do some experimentation and report your findings!

Try airlayering, it worksbut with patience, cause small stem

OP - did you sort out a succesfull rooting method?

I have never heard of this species but if they are known to be difficult to root as cuttings, then that will mean that even if you have a wonderful heat bed, perfect misting system, correct temperature of air (without awful breezes blowing on the plants) use a good cutting mix, clean everything before use and practise good hygiene everywhere, they will still be difficult to propagate from cuttings. (Very frustrating.)

Perhaps they are commonly grown from seed.