If you want a great finished drywall job, you need to start from the base up — a good level surface, carefully hung drywall, and a good taping job. But after all that work, make sure you finish it off well with a great sanding job. Here are some tips to finish up perfectly.
Let there be light. The walls might look nice and smooth, but once the paint goes on or the light shines the wrong way, look out. The trick is to find the flaws now. Set up bright work lights to shine on the seams from an angle close to the wall. This creates shadows where the seam bulges or sinks. Mark the spots that need attention with a pencil — “L” for “low” or “H” for “high”. You can also find bulges using your widest drywall blade. Hold a 12″ blade perpendicular to the wall at the seams, with the light shining from behind, and you can quickly spot prominent bulges and depressions.
Once you’ve marked all the spots, give it a once-over, carrying a light with you and shining it on seams from various angles. Double-check with your drywall blade. If you see small gouges here and there, circle them with your pencil for filling later.
Now that you’ve mapped out all the areas that need attention, fill in the low spots and the gouges with mud, using your 12″ blade.
Sand the high spots, checking the bulge often so you don’t go too far. Keep your worklight on the area you’re sanding, so you can monitor the excess.
Where the surface is already level, just give it a very light sanding; this is simply to remove the smooth, glossy surface of the dry mud, so it won’t show up after painting.
More sanding tips next.