A photograph would help to get an idea but it sounds like it should be sanded/filled/primed/undercoated and 2 top coats which is a lot of work but all pretty normal for decorators.
I think peel stop is a good idea but personally I can't see any quick way to properly decorate that. I would be thinking sand it off then prime with B.I.N. Aqua and 2 top coats. That's my lowest standard!
A photograph would help to get an idea but it sounds like it should be sanded/filled/primed/undercoated and 2 top coats which is a lot of work but all pretty normal for decorators.