Airlayering is rarely done in plumeria. If (as I suspect from your location) it is spring where you are, I would recommend taking the cuttings, letting them callous for a week in a shady but well-ventilated space, and then planting them in a well-draining soil.
The main plant will put out new shoots from the old leaf scars so you could have 4 plants when all is said and done
