Paint peeled in a few areas I'm assuming from bad prep many years back, and no primer. Should I go ahead and sand/prime these areas before mudding and repairing? The exposed plaster is super slick and very smooth. Sorry if this is a subjective question, I'm simply trying to understand IF primer is recommended before repair, or just go straight to mud coat (Easy Sand Joint Setting Compound, or Plus 3 Pre-Mixed Compound) and then prime after.
This surface is going to be painted with a standard 3/8" nap roller after to give it a slight roller texture, so it won't be left as smooth as the plaster is, and instead will have roller texture.