Open your premixed vinyl drywall patching compound and mix it thoroughly. Use a two inch drywall knife to scoop a small amount of compound out of the container and apply it to the crack, pushing it in and dragging the flat end of the drywall knife blade across the wall to level it, and scrape away excess.
Allow the patching compound to dry completely. Use a damp sanding sponge to sand down the patched area until it is level with the surrounding wall. Wipe remaining dust from the wall with a damp paper towel.
Brush a coat of latex primer over the patched area with a soft bristle paint brush. Leave the primer until its dry to the touch. Apply a coat of paint in the color of the surrounding wall with a clean paint brush. Feather the edges out into the surrounding paint to make the outline of the painted area less noticeable.
Cut a piece of plastic drywall repair mesh to fit the crack. Use scissors to round off the corners and press the self adhering mesh to the wall, so that it covers the crack and extends onto sound drywall on all sides.
Apply the patching compound over the mesh, filling the crack and piling it up to cover the mesh. Use a 6 inch wide drywall knife to spread the compound, feathering the edges down to meet the surrounding wall surface. Allow it to dry and add a second coat if needed to fill any gaps. Allow this top coat to dry overnight.
Sand the area lightly to smooth the compound and blend it into the surrounding wall. Apply primer and paint as described in the first section.