I just propagated 8 Plumeria cuttings and it's such a simple process. I documented how I did it so if you follow these steps carefully then you should be able to do it with at least a 90% success rate.
Saw this on the sidewalk and saw an opportunity!
Removed all leaves and used a sharp knife to cut individual branches
Keep Cuttings in a cool dry place for 3 days to allow the ends to callus over.
They Should Look like this
Apply rooting hormone Generously to the cut end
This is the magical sauce I use. It's a purple liquid.
Punch a hole in the potting soil just a little wider than your cutting. Plant your cutting deep enough so that it doesn't fall over. (make sure the rooting hormone doesn't rub off when putting it down inside) Use a well draining soil, I used Miracle Gro Moisture Control potting mix. The better soil you use, the better chance you have at this working.
Pat soil down firmly ensuring good contact with the cutting. This also prevents the cutting from falling over.
Water them and place them in a sunny location. Remember * Don't kill your plumerias with love.* Be patient and they should start getting leaves.