Did some digging online and the secret is a dish of moist O²-rich soil inside a loosely sealed clear tote. The clear tote lets the leaves photosynthesize while maintaining a higher than average temp and humidity. Meanwhile the oxygenated soil helps with root production.
The mix I used here is: 1 part fast draining soil mix 1 part sphagnum moss
I used a hose sprayer to moisten/oxygenated the soil every few days. The process took about a month for root development, and I lost 2 props in the process. Heat helps here, I'm in USDA zone 5b and I kept them shaded under my jade tree and a canopy in the yard.
These plants are very cool and seem to be easy to grow, if you have a mature-enough specimen for propagation, use the oldest and lowest leaves for propagation, as they likely produce the least from photosynthesis and will have the stiffest/hardiest stems.
I recently tried putting ficus cuttings in water and was surprised at how quickly they made new roots. They are now potted and grow pretty fast