Begin by filling any holes or dents in the surface with drywall joint compound.
First, use the drywall knife to scrape off any tags of paper around the hole.
Then use the handle to indent the area around the hole before skimming over the holes, depressions or gaps between wallpaper seams.
When the joint compound is dry, apply a coat of oil-based primer over all the wallpaper’s surface. This will help hide the wallpaper pattern and it will create a better surface for the finish paint to stick to.
After the primer is dry, it may be necessary to apply a little more joint compound to difficult areas.
Finally, apply the topcoat – and begin enjoying the space.