Use sheet and 2 inch masking tape to help confine dust to the work area . Cover all door ways , cabinets , built ins , and any gaps or other openings with plastic , sealing all four edges with tape ; otherwise the fine dust produced by sanding can find its way through.
Knock down any ridges , chunks , or tool marks prior to sanding , using a six-inch taping knife. Do not apply too much pressure you do not want to dig into the compound , only remove the excess.
As you work , if you oversand or discover low spots that require another coat of compound , mark the area with a piece of tape for repair after you finish sanding . Make sure to wipe away dust so the tape sticks to the surface.
Lightly sand all seams and outside corners using a pole sander with 220 grit sanding screen or 150 grit sandpaper. Work in the direction of the joints , applying even pressure to smooth transitions and high areas. Do not sand out depressions fill them with compound and resand. Be careful not to overland or expose the joint tape.
Inside corners often are finished wit only one or two thin coats of compound over the tape . Sand the inside edge edge edge or joints only lightly and smooth the outside edge carefully , inside corners will be sanded by hand later .
Fine sand the seams , outside corners , and father heads using a sanding block with 150 to 220 grit sanding screen or sandpaper . As you work, use your hand to feel to defects along the compound . A bright work light angled to highlight seams can help reveal problem areas.
To avoid damage from oversanding use 150 grit dry sanding sponge to sand inside corners . The sides sanding sponges also contain grit, allowing you to sand both sides of a corner at once to help prevent oversanding .
For tight or hard to reach corners, fold a piece of sanding screen or sandpaper int thirds and sand the area carefully. Rather than using just your fingertips, try to flatten your hand as much possible to spread out the pressure to avoid sanding to deep.
Repair depressions , scratches, or exposed tape due to overspending after final sanding is complete. Wipe the area with a dry cloth to remove dust, then apply a thin coat of all purpose compound . Allow to dry thoroughly , then resand.
With sanding complete , remove dust from the panels with a dry towel or soft broom . Use a wet dry vacuum to clean out all electrical boxes and around floors, windows, and doors, then carefully roll up sheet plastic and discard . Finally, damp mop the floor to remove andy remaining dust.
For experts using the wet sand will cut down on dust and barriers possibly if really use 20 minute compound and mix really well.