The main areas that require skill and patience while doing this task are the seams, screws, and corners. So, do not carry out this home improvement project in haste, take some time over it, so that you get the best results.
To finish a drywall, you will need at least 3 coats of mud or joint compound, as one coat does not help. Why? Because, mud shrinks as it dries, therefore for an even look, you need to apply more coats.
You will need tools like gloves, goggles, old clothes, mud, one mud pan, a roll of drywall tape, flat drywall knives of various lengths, and a metal corner spreader. Given ahead are the instructions that need to be followed while applying mud to your newly installed drywall.
Measure the length of each seam and take some mud on a metal spreader and coat the center of the seam, covering its entire length so that a uniform layer of one-fourth inch is formed. Cut tape as per the length of the seam and paste it over the applied mud with a gentle hand.
Flatten the tape properly using the knife, so that the excess mud comes out of the seam. Let it dry overnight. Apply another coat of mud on the seam covering the width of the tape. This step should be repeated once the second coat dries. When all the three coats dry properly, sand the mud to get a smooth and even surface.
Put mud on the tape so that it forms a thin layer of about an inch. Spread it up to 2 inches on both sides of the corner joint. Once the previous coat dries completely, apply 3 coats of mud on it. The outside corners of a drywall consist of fiberglass or metal corner beads which are fitted with nails.
Add the first coat of mud on the corner bead and spread it over 4-5 inches away from its edge. The next coat has to be extended to 6-8 inches and the final one should cover 10-12 inches.
Take small amount of mud on a knife and smear it over the screw heads covering them completely. Do not use excess mud as it will form lumps on the drywall. Allow the mud to dry overnight and apply another coat on the next day. This should be repeated 3 times or more until the screw holes have sealed.
Always remember to wait for each layer to dry completely before applying a new one. Also, always apply multiple thin layers instead of just one thick one.