Open the container of drywall mud. Using your mud masher, mix the mud to remove any air pockets, as well as to blend the mud evenly.
Transfer some of the drywall mud into your mud tray using the drywall knife. Mix the mud once again once it is in the mud tray, using the drywall knife. The consistency of the mud should be smooth and soft.
Apply a coat of drywall mud to the screw holes first. Scoop the mud using the drywall knife and then drag the mud across the screw holes. Remove the excess mud with the drywall knife and continue the process until all screw holes are covered.
Place a thick layer of mud on the seams between two boards of drywall. Run the drywall knife down the length of the seam, ensuring that a smooth coat of mud is applied to the seams.
Allow the mud to dry. Drying times will vary among types and brands of mud. Refer to the container for specific drying times.
Sand, scrape and scrub the mud to ensure a smooth surface once it has dried. Once smooth, the ceiling will be ready for painting.