Use the flat edge of a trowel to spread a thin layer along the seam and force it into the gap between the panels. You can apply drywall tape if you want, but this is not necessary since you are not covering screw heads the way you do with drywall. If you apply tape on the mud, spread another layer of mud over it to cover it. Let the mud dry overnight.
The tapered drywall joint results in nearly invisible seams because the mudding compound perfectly fits in the "valley" and does not rise above the level of the drywall facing. With the tapered drywall joint, you can even use a stronger type of tape, such as mesh fiberglass drywall tape.
Load bearing corners will often have bellied out areas in the metal corners. Short of replacing the whole corner bead, I would take a hack saw and saw a kerf through the bead to remove the tension. Then put drywall screws on both sides of the cut to firm up the metal corner, then just apply drywall mud in the normal fashion. A slight lengthwise factory-made crease in the paper helps you fold it down the middle when using it for inside corners. Paper tape takes some skill to learn. You need to first prepare the wall with a thin strip of drywall mud, a process known as bedding. STEP 1: Mix mud, Spread. Mix up your joint compound (With water) until it is thin enough to work with. For more on mud and how to mix go here All about Joint Compound. Using a drywall pan and a 10" knife, spread a nice even bed of mud on one side of the corner bead. Try to go from the ceiling down a little past half way. This makes any change in angle from the tape more gradual. And when installing the tiles, you use a notched trowel that gives you room to adjust the level of each tile. Typically, I'd recommend a caulk in the corners between the tiles (matching the grout color if possible) since grout will crack as the two surfaces shift over time.
Drywall Mud Drywall Finishing Drywall Repair Drywall Tape Home Remodeling Diy Home Renovation Drywall Corners Hanging Drywall Home Fix A skilled taper can hide a lot of mistakes left behind by framers and drywall hangers. Step 1 Measure the area where the new drywall will be installed. To get the square feet of the area, measure the width and height and multiply the two numbers. A standard 4-by-8 sheet, for example, measures 32 square feet.