I live in an old house built in the 1920's. My bedroom used to be the attic and I wanted to remove old wallpaper and replace with paint. the material under the wallpaper was a painted surface, which came off in flakes when scrapping the paper off. Under that seems to be some sort of composite (no plaster or sheetrock). Now I have an unsightly surface that will not be a smooth surface even after painting. Any suggestions?