Remove any fixtures, switches or outlet face covers and any other non permanent wall items. Wipe the wall surface with a damp sponge to clear away any substances, grease or oil.
Apply painter's tape over any baseboard molding or door and window trim. Lay a drop cloth over the floor to protect the floor covering from dripping joint compound.
Slide a light-nap paint roller onto a standard size paint roll tool, then screw an extension pole into the threaded bottom hole of the roller tool.
Spoon premixed joint compound into a 5-gallon bucket and slowly mix with water. Stir it with a stir stick and add water until it has the consistency of latex paint. Ensure that there are no lumps and that it is perfectly smooth.
Pour the thinned joint compound into a standard paint tray. Remove any clumps of compound that you see in the tray after pouring.
Hold the roller pole at an angle with both hands and set the roller into the tray. Work the roller back and forth through the compound to fill the nap. Place the roller onto the wall quickly to minimize the amount of compound that drips.
Start at one high corner and slowly roll the joint compound downward to the baseboard with very light pressure. Work evenly across the wall, smoothing the seams between vertical strokes with the roller before the compound dries.
Wipe away and smooth any drips of compound on the wall and allow the surface to dry for at least two hours.