My husband and I just had to tackle this problem in the kitchen. We live in a house that was built 25 years ago and the previous owner (builder)had panels in the kitchen which he used some kind of adhesive that was very rough and bumpy. It was easy removing the panels but the adhesive was tough to get off. We sand it down with a sanding machine as much as we could and then we put on a light coat of plaster. We will have to sand it a little after plastering but over all it is very smooth.