Drywall joints need to have drywall tape and joint compound, or mud as it's often called, applied to make it smooth. The goal is to make an invisible seam.
Prepare the Mud
Put some mud in the mud tray instead of working straight out of the bucket of mud. This will keep debris out of the mud in the bucket. Make sure the lid is on the mud bucket tightly so that it doesn’t dry out.
Level Nail Holes
Fill in any nail holes with the mud. Use the mud knife to scrape the mud down level with the drywall surface.
Apply the Joint Compound
Use the 4” drywall knife and put a layer of mud on the entire joint.
Apply the Tape
Put the tape over the mud and push it into the mud. Then, immediately apply another layer of mud over the tape. Cover the whole piece of tape. Scrape the drywall knife over the mud to push out any excess mud. You want the tape to be flat against the seam without any air pockets
When you come to an inside corner, apply a layer of mud into the corner joint. The drywall tape is pre-scored to fold in half. Fold the dry piece of drywall tape in half to emphasize the fold. Put on a layer of mud on each side of the corner. Then, put the tape over the corner seam, pushing it into the mud. Apply more mud as needed on the sides of the tape. Scrape away the excess with a corner knife made especially for that purpose.
In order to protect an outside corner, you must apply a metal corner strip. You simply cut it to fit the height of the wall. Nail it in every 6 inches. Apply mud over the corner, smoothing it with the drywall knife. Feather the mud out from the corner to the drywall.
Let the mud dry completely. It can take from 8 to 24 hours and can be sped up by using a fan.
Sand the Surface
Scrape off any excess dried mud with the drywall knife. Use a sanding block to smooth out the first coat of mud. A dampened sponge can do the final smoothing. Don’t use too much water or rub off the drywall compound.
Apply a Second Coat
The second coat of mud should be thinner. Use a 6” drywall knife to apply this coat. Let it dry and sand it down. If the wall will be textured, then you can stop at two coats.
Apply The Third Coat
The third coat of mud is thinner than the second. Use a 10” drywall knife to apply the mud. Let it dry and sand it down.
Inspect the Walls
Now check the surface of the wall to look for any uneven areas or imperfections. Using a flashlight held at different angles can help you to see what you missed. Once you are satisfied with the wall finish, you are done.
This project takes a lot of patience and some time, but you will be able to enjoy your perfectly finished walls for years to come.