Once you have the drywall in place, it is time to fill in the area between the seams. Sanding drywall is a big, messy job. You can finish the drywall without having to sand the surface. By using a rubber float or a knife, you can smooth the wall down so it looks like you spent the day sanding. It takes time to do the job properly.
Prepare your drywall before you mix and apply the joint compound to the seams. Apply drywall tape to cover the seams on your drywall. Begin at the top of the drywall seam and continue until you reach the bottom of the drywall seam. Press the tape as you go, to make sure it is smooth without any puckering or air bubbles.
Mix joint compound according to manufacturer's directions. Only mix as much joint compound or mud as you can use in 15 to 25 minutes. If the compound becomes hard, you cannot make it soft again. If you add more water to make it pliable, you will weaken the mixture. In this state, it will not stick to the wall.
Spread a thin layer of the joint compound over the drywall taped seams using a drywall knife. The joint compound should cover the drywall tape and extend 2 inches beyond each side of the drywall tape.
Allow the joint compound to harden on the wall. This takes between 8 and 24 hours depending on the amount of humidity in the air.
Sponge a little water onto the joint compound. The joint compound has to be a bit wet before you can work it smooth.
Take the rubber float or a 10-inch knife that you have wetted down and glide the edge across the top of the joint compound. Hold the knife or rubber float at a 90-degree angle; only the trailing edge of the trowel should touch the compound. Apply pressure on the knife or rubber float as you pull it up or down in one continuous stroke. Do not have the entire bottom of the rubber float touching the joint compound.
Keep stroking the rubber float across the patched area until you make it smooth.