Measure the stud wall from one end out to the last stud within 8 feet. Take the measurement at the middle of the edge of that stud.
Transfer the measurement to a sheet of drywall, drawing a line across the 4-foot span of the board at the correct distance using a level and pencil. Score along the line with your utility knife. Bend the piece at the scored line until it breaks.
Press the cut drywall to the wall, sitting on the floor. Shoot drywall screws every 6 inches through the drywall and into each stud behind it using your screw gun.
Repeat the process to measure and cut sheets for the rest of the wall. In horizontal courses, build up the wall course by course. Arrange the courses so there are no four-way intersections.
Spread a line of joint compound over the first seam between the drywall sheets using a drywall knife. Make the compound line about 4 inches wide and very thin and smooth.
Press a strip of paper drywall tape into the compound, covering the whole seam. Spread a second line of compound over the tape, so the tape is embedded. Squeeze the knife over the tape to push out all the excess compound and get the tape smooth and flat.
Let the compound set for six hours. Spread on a second layer of compound, making it about 2 inches wider than the first layer. Let it dry six hours.
Spread on third layer, again making it about 2 inches wider than the previous layer. Let it dry 12 hours.
Sand the dried compound flat with a drywall sander. Repaint the wall.