*Always wear a dust mask when sanding joint compound or otherwise dealing with sanding dust*
When it comes to sanding dry joint compound you're going to have a lot of dust. And because it's so light the dust will float through the air and get on every exposed surface. This can be the most difficult part of doing wall repairs or hanging new drywall for some people. The good news is there is a way to greatly reduce the dust produced by sanding joint compound. The bad news is you may need to buy a new tool or two to do it. If you already have a good shop vac you're half way there. If not you may be able to rent one or you can use an old house vacuum if you don't mind getting it dirty or maybe damaging the motor over time.
Because joint compound dust is very fine you will need a good filter in the vacuum cleaner to contain it. This means your shop vac should have a pleated filter, not a foam or paper filter. If you don't use a good filter the dust will surely ruin the vacuum cleaner motor in a short time. If you have a lot of sanding to do, you will have to clean the filter as it becomes clogged with dust. If the vacuum begins to sound strained, check the filter and clean it if necessary. If you have a big sanding job you should have a replacement filter so you don't have to stop in the middle to clean the vacuum.
To clean a dust filled shop vac filter, take the whole thing outside if possible. Remove the filter and immediately place it inside a large plastic trash bag. Close the top of the bag around your arm while still holding the filter, to contain the dust. Shake the filter and tap it against a firm surface to loosen the dust. Be careful not to crush the pleats. With the bulk of the dust removed, take the filter out of the bag and place into a new one. Close the first bag to hold the dust. Work with the filter in the bag and use a screwdriver and hand broom to loosen and remove clinging dust from between the pleats. Shake the last of the dust from the filter or if you have a blower you can use it to remove even more dust. You can wash the filter and let it dry overnight or you can reinstall it onto the shop vac.
With your vacuum ready the second part of this sanding miracle is an attachment that allows the vacuum to draw dust away as you sand.
The "DustDog®" made by Hyde® is the only tool of its kind we've found on the market. This sanding attachment will make most drywall sanding jobs much less taxing. It comes with a plastic block with holes feeding an outlet tube. The rubber base accepts sanding screens (one is included in the package) and a six foot hose with adaptors, connects with your vacuum cleaner hose to provide about 12 feet of reach. The whole thing is very light so using it is as easy or easier than sanding by hand with folded sandpaper.
While this sander is sufficient for most jobs around the house, if you're installing all new drywall on walls and ceilings or doing extensive plaster repairs, they also make a DustDog® with a pole attachment that can make these big jobs easier.
Before beginning the sanding part of your drywall finishing job, be sure to let the joint compound dry completely. Load the sanding screen onto the block and tighten it so it lays centered and flat over the holes in the block. Fold the edges of the screen up around the sides of the block to form a square for sanding corners.
Hook the hoses together and attach them to the vacuum cleaner. Turn the vacuum on and begin sanding at a corner or the edge of a repair. Apply only enough pressure to begin removing the surface of the patch but not enough to dig in too deeply with the screen. Go slowly enough to allow the vacuum to do its job.
Move the sander lightly, in arching strokes, to remove enough compound to sand out scratches, pits and gouges in the surface. Use the edge of the sanding block with the folded screen to get into wall corners and along ceilings to finish drywall. Go around the edge of repairs, paying close attention to blending the surrounding wall surface and the dry joint compound together in a smooth transition.