DIY Doctor UK DIY Forums

I am in the process of remodeling my master bath. I have removed all the wall paper with steamer. Under the wall paper, I found a thin coat of paint or some simliar material. In a lot areas the thin layer was removed with the wall paper. I have gone back and skimmed those areas with mud. I have sanded the area smooth. My question is should I skim the whole wall or just proceed with a sealant, primer and then paint. I do have pics available if needed.
Bill