Stripping wallpaper is a tedious endeavour, and more often than not, leftover adhesive residue remains attached to the wall even after the paper is gone. This adhesive greatly interferes with paint adhesion and will cause paint to separate into what is known as a crackling effect. If you have worked hard to remove your wallpaper adhesive but were unable to clean it away entirely, you will need to apply a specific type of primer to the wall before you paint, or you will have no chance at adhesion.
Cover flooring adjacent to the walls with dust sheets.
Fill a spray bottle with soapy warm water.
Spray the wallpaper adhesive with the warm water, and scrape away as much of the glue as possible, using a plastic putty knife. Allow the wall to dry completely.
Coat any remaining wallpaper adhesive with an oil-based primer, using the paintbrushes.
Allow the primer to dry for two full hours, and then apply two coats of paint using a roller. Allow two hours of dry time between coats.
There are specific products available at paint and home improvement stores formulated to remove wallpaper adhesive. However, these products generate toxic fumes. Be sure to open windows to provide ventilation if you choose to use these solvents. Apply a tinted oil-based primer if you plan to paint with a dark paint. Apply a white primer if you plan to paint with light colours.
Do not prime over wallpaper adhesive with a latex primer. Do not use a latex paintbrush to apply an oil-based primer. Do not use a metallic putty knife in place of a plastic one, or you may gouge chunks form the drywall. Never use diluted bleach to remove wallpaper adhesive, as the runoff may damage carpeting and baseboards.