These instruction cover finishing drywall seams with paper drywall tape and ready–mixed joint compound. To finish drywall seams with fiberglass mesh tape use these instructions. To install drywall corner bead use this link, finish inside drywall corners here and use this link for more about drywall finishing materials and techniques.
Use ready–mixed joint compound for this job, setting–type will get hard too quickly and may cause problems.
Unroll the paper tape along each joint to be finished and cut it a little longer than the required length. Cut the paper squarely using a joint knife as shown to press firmly while pulling back quickly on the tape to tear it.
Use crossing strokes with the blade to apply a coat of joint compound about ½in thick over the seam.
Lightly press the tape into the mud, placing it squarely at the corner and pulling it out along the remainder of the seam. Cut the tape off squarely at the other end of the seam where it will be hidden by trim molding or where it joins another seam.
Hold a 6 inch joint knife at about 30° and starting a few inches from the corner, draw the knife along, pressing hard against the tape to squeeze out all but a thin coat of mud from between the wall and the paper. Go back over the same space a second time to be sure you squeeze as much mud as possible from under the tape without tearing it.
Skim back in the opposite direction to finish to the corner and then work down the seam to the other end. Return the excess mud to the rim of the pan as it collects on the knife blade. Go over the edges of the mud to skim off any buildup there.
Apply a second coat of mud to the seams when the first has set firmly. Use a larger joint knife in crossing strokes to cover the tape and fill the depression between the drywall sheets with excess mud.
Skim the excess mud from the joint resting the knife on the high point along each side of the depression, while "floating" the blade over the center to level it with the surrounding wall. Don't press too hard on the center of the blade, this will cause it to bow and create a perceptible dip in the finished seam. Allow the mud to dry and repeat this step as many times as needed to completely level the joint.
Check for a level joint by holding the knife perpendicular to the wall surface while looking for any gap between the blade and the wall, indicating the depression is not quite level. Apply a third or fourth coat of mud if necessary to smooth the joint. Let the final coat dry for 6 to 12 hours and lightly sand with medium grit sandpaper to finish the job.