Examine the wall to make sure all screws and nails are set slightly below the surface. Run the flat edge of a clean drywall knife over the surface of the wall. Listen for anything that catches on the knife.
Attach a corner bead to the outside corners with screws. Keep the screw heads slightly below surface level.
Center self-adhesive drywall tape along the seams in the drywall. Cut the tape so it butts up against adjoining tape but doesn’t overlap it. This helps create a smoother wall. Run the flat edge of a drywall knife along the length of the drywall tape to seal it to the wall.
Thin out pre-mixed drywall mud with a paddle mixer attached to a drill until the mud is the consistency of cake icing. Don’t over-mix it or the mud may form tiny bubbles that are hard to work out.
Cut paper drywall tape to the length of each corner. Fold the paper in half lengthwise. Apply a thin coat of drywall mud to both sides of the corner joint. Set the paper in place with the fold in the corner. Use a drywall knife to smooth the paper in place over the mud layer. Expect to see mud oozing out from under the tape. Feather any excess mud onto the wall’s surface. Repeat this process for each of the room’s corners.
Apply a thin “tape coat” layer of mud over all of the tape and screw heads with a drywall knife. Take care to keep all surfaces as smooth as possible. Allow this layer to dry.
Add a wider “fill coat” layer of mud with a wider drywall knife. This layer is also thin and extends farther on either side of the tape. Allow this coat to dry.
Apply the “finish coat” layer with your widest drywall knife. This last coat should provide a smooth wall surface when it dries.
Sand down any uneven surfaces with 150-grit sandpaper. Remove the grit with a tack cloth.
Prime the drywall surfaces for painting with a primer specifically designed for drywall. Paint the edges of the room with a paintbrush then cover the rest of the walls with a 1/2-inch nap roller. Let the primer dry. If you still see light and dark spots that show the drywall tape underneath the primer, apply a second coat. Once you finish the primer coat, you are ready to paint the walls.