One of the main trunks (about 3 inches in diameter) broke off in high winds when I had jade outside in summer. I cut the branch off low to the base. It has not healed and has greenish mold on surface of cut. I repeated this with a lower cut and mold has again appeared. There is only about 2 inches left to cut off above soil level.
How do I prevent, or reduce chances, of mold forming if I cut again.
BTW, this is a 42 year old jade (which has given me many offspring). I keep the jade outside in the summer and inside in the winter.

You might try sprinkling the cut area with cinnamon powder. Cinnamon is a natural fungicide. I keep a container of it with my gardening supplies.