When you’re working with drywall, cleanliness makes all the difference in the appearance of the final job. Continually clean your tools and mud pan with a coarse sponge and bucket of water.
To run inside corners:
Using your four-inch wallboard knife, apply a continuous bed of drywall compound to each of the two surfaces. Make sure to place a sufficient amount of material at the joint of the two walls. Using the paper-style drywall tape, cut a piece the proper length to run from floor to ceiling. You will find that this drywall tape comes with a crease down the middle. Fold the crease to fit your inside corner the entire length of the tape. Using slight finger pressure and working from the top down, adhere the tape to the drywall compound.
Again, starting from the top with your four-inch knife approximately 30 degrees off the wallboard surface, smooth one side of the tape to the wall. Repeat the procedure on the opposite wall. Be careful not to squeeze all the mud out from behind the tape; light pressure is all it needs. Keep the crease of the tape tight to the inside of the corner. Use a six-inch knife to remove any ridges or irregularities in the work. This will require two more coats of mud with sanding in between each coat, so don’t overwork the corner. Allow it to dry overnight.
To run outside corners:
Several types of outside corner bead are available: the metal 90-degree corner bead; the metal bullnose; and the paper bullnose. The most common is the 90 degree metal. If you’re a beginner, don’t nail this bead to the wall. It’s hard to get straight when you are learning, and most people will dent up the bead with their hammers.
Instead, “tape” the corner bead on. Using your four-inch knife, run two continuous beds of adhesive on each surface of the corner. Then bed the corner bead into this material. It will slip and slide a little bit, so just work it until it is straight, plumb and secure. Now run another four-inch bed of joint compound and imbed a strip of the drywall tape over each leg of the corner bead. Smooth this out with your four-inch knife using the outside head of the corner bead as a screed. Apply two more coats of mud, and sand in between. Always allow a coat of mud to dry overnight, remembering to sand or sponge it before applying your next coat.