Buy a latex product called Shields. It is a wallpaper primer. Even if you paint the walls instead of re-papering this product works. Has lots of pigment and dries hard. Sand it after drying, put drywall mud where necessary. Sand again when mud is dry. Paint with egg shell paint, or flat finish. Ps.. Two coats on small bathroom ceilings along with the walls to be papered works as good as kilz or regular ceiling white.