A: A great question. Unfortunately, plumeria slips can go soft, or even moldy relatively quickly. If you find that yours suffers from this malady, all is not lost. Simply cut off the mushy or moldy part. To be on the safe side, cut about an inch higher than the bad part. The cut will cause the bottom of the stalk to drip a semi-sticky white sap.
(Try not to get the sap all over you. Some find that the sap irritates their skin slightly)
Let your cutting dry out for about one week. If you've detected no further problems (e.g. the good stalk hasn't itself gone mushy, then you're good to go. Plant away!