Once your wall is prepped it’s time to get to the real work. Sanding is about precision and persistence, don’t get ahead of yourself or go at it too hard initially because any large mistakes you make will need to be corrected later.
If the dust is causing a ton of problems, there’s a simple way around it: wet sanding. If you do things this way you’ll need a bucket of water and to periodically dip the sanding block or sponge you’re currently using in the water. It’ll also save you on paper over the course of a long job.
Wet sanding is for walls that are going to be textured otherwise you’ll have to come back over it with fine paper once you’re done.
Either way, the process is pretty much the same. Rub the paper along the mud using a circular motion, making sure to get everything as flat as possible. More than flat, you’ll want to make things smooth. This will help to ensure that the paint you lay on it looks good, as opposed to a bit rough.
The smoothness is the part that people have the hardest time with, and for good reason: it requires a precise eye for detail. Flat is one thing, but truly smooth is a whole different ball game.
Smoothness will come from light pressure and semi-random strokes. There’s a reason that DA sanders have a reputation for making the smoothest possible surface in a short time: the random orbits of the sander prevent the marks that will come with repeating the same stroke.
As far as pressure goes, if you’re pulling flakes as opposed to dust off the wall you’re pressing way too hard. All it will do is make sure you have to replace the paper on the block quicker, and possibly make you lay another coat of mud.
In order to achieve the right motion for sanding, trying out a spiral pattern is a good way to do things for most people, especially those worried about not getting it right. Start small and move clockwise in concentric circles while moving along the wall, then reverse the motion and move back.
Don’t just use left/right or up/down sanding, it’s counterproductive and won’t do you any favors since it’ll leave large marks on the wall.
Use the sponge for inside corners, it’s squishy make-up will allow you to take care of them quite easily. They’re also good for outside corners, especially if you’re planning on a slight rounding as a matter of aesthetics.
It all sounds simple, but trust us, you’re going to be there all day. It will get tedious, try playing music and remember to take breaks. If you’re dry sanding take them a little bit more frequently, the dust can build up in the air and allowing it to settle will make things a lot easier on you.