Use a special sanding tool
Use a hand sander and precut sandpaper
Use a hand sander ($6), a package of 150-grit drywall sanding paper that’s precut to fit your sander, and a sanding sponge for corners and detail sanding. You’ll also need a double-strap dust mask rated for nuisance dust and goggles to keep the dust out of your eyes. A hat or scarf to keep the dust out of your hair is a good idea too. Sand with light pressure along the edge of seams and around screws to avoid “fuzzing” the drywall paper. Sand the center of seams just enough to remove ridges and bumps.
Choose fine sandpaper for the best results
Heavy-grit paper will leave sanding marks
It’s tempting to buy 80-grit paper to speed up the sanding job. But because modern lightweight joint compound is so soft, you don’t need heavy-grit paper to sand it. Coarse-grit paper or sanding screens will leave undesirable sanding marks. We recommend precut sheets of 120-grit or 150-grit paper for the best results. Make sure the paper is taut by first anchoring one end under the clamp. Then push the other end under the other clamp with one hand while you tighten the clamp screw with the other.
Fill gouges—don't sand them
Use joint compound to fill depressions
Don’t try to sand out gouges and big ridges. It’s much easier just to trowel on another coat of joint compound. This is especially important at the edge of joints, where too much sanding will damage the paper face on the drywall. It’s quick and easy to trowel a thin coat over the edge of the seam to fill a depression. Touch up grooves and large ridges with another coat of joint compound rather than trying to sand them out. It may take a few coats to fill deep grooves.
Spot problem areas with a handheld light
Then mark problems spots with a pencil
Do a once-over with your hand sander, making sure to hit every surface with joint compound on it. Keep a pencil handy to mark problem areas that need filling or detail sanding. Then get a handheld lamp and go back over the job while shining the light parallel to the wall surface. Use your hand sander and sponge sander to touch up trouble spots. Mark depressions and other spots that need filling. Finish the job by filling the marked areas with joint compound and finally sanding these spots when they dry.
Prime the walls, then sand again
Repriming removes fuzz and lumps
Sanding after priming is a critical step that most beginners skip. But sanding at this stage removes paper fuzz and lumps that will show through your paint job. This is also the time to take care of other imperfections by filling them with joint compound. Don’t forget to sand and reprime these touched-up areas or they’ll also show up when you paint the walls. Prime the walls and sand them lightly after the primer dries to remove paper fuzz and lumps.
Use a sanding sponge for corners
Hand sanders gouge corners easily
Sanding inside corners with a hand sander is asking for trouble. In the first place, it’s difficult to get a crisp corner. But even more troublesome is the tendency to scuff or gouge the opposite side of the corner with the edge of the sander. It’s OK to sand within a few inches of the corner with your hand sander. Then go back and touch up with a sanding sponge or folded piece of drywall sanding paper.
Sand with a light touch
Use moderate to light pressure
Even though using a hand sander is straightforward, the drywall pro we talked to offered these helpful tips. Use moderate to light pressure and avoid sanding over the same spot in a straight line. This can leave a groove or depression that will show up when you paint. Instead, move the sander around on the joint as you sand. If you do sand too much in one spot, touch it up with joint compound and resand when it dries.
Angle the sander slightly
Keep the sander angled slightly. Press lightly and avoid scrubbing back and forth in one spot. Don’t sand over electrical boxes or other openings. The edges of the box can rip your sandpaper, or a piece of the paper facing on the drywall can roll up under the sander and tear off. Keep a few inches away from electrical box openings and touch up around them later with a sanding sponge.
Wet-sand joints to limit dust
To limit the dust, consider wet-sanding the joints. Tape with care so you don’t have to do much sanding. Then buy a big flat drywall sponge ($2 at home centers), wet and wring it out, and simply wipe smooth any minor flaws. You probably won’t have to use the coarse side of the sponge unless you have unusually rough areas.