Different Layers After Stripping Wallpaper Banner off

[Kat660]

I have stripped a wallpaper banner in my bedroom, which went round the middle of the walls all around the room. I have stripped it all but it has left different layers and patches here and there. Part of it would be left with 2 different paint layers or it would gone back to the plasterboard. How can I fix this without getting a plaster in or whatever. As it is in the middle of the walls. And not the whole wall. Can I use easi fill and skim on the area all around, prime it with a watered down emulsion or pva then sand and paint. Or is there something i can use like poly filla smoothover and paint once dried? Whats the best and easiest solution?