I recently bought a flat that needs a complete overhaul. I've stripped the wallpaper and scrubbed the walls to the point where they're flat, but they're still covered in a layer of old, dusty paint which comes off on your hands when you touch it but is a real pain to get off entirely.
Do I actually need to remove it, or is there some sort of primer/sealer I can use before painting? If I do have to remove it, is there some cheat I can use rather than just chugging around it with a sponge and a bucket of water?