The Drywall Mud

• Use either a setting type joint compound, which comes as a powder that you mix with water, or a ready-mix joint compound. The ready-mix compound comes in a bucket and is often used as a means of skipping the mixing phase, but sometimes it needs a little water added to it also. To skim coat over small areas, such as a dent or crack where you will only need to apply one or two layers, use ready-mix. To cover larger areas and areas with moisture damage, use the setting compound. With setting type compound, mix up only as much as you can use in the time allowed before it dries. Consult the manufacturer's instructions for the specific drying time, which can vary from 20 minutes to several hours.
  
  

Reverse Your Direction

• When you apply the second coat of mud, stroke the mud in the opposite direction that you did for the first stroke, which helps you achieve a smoother finish, especially if the wall surface has a wavy texture. For example, use vertical strokes with the drywall knife to apply the first coat. Apply the second coat of mud with horizontal strokes, which helps to level any ridges and fill any irregularities in the surface. With each new coat of mud, reverse the direction you used with the last coat.
  
  

Sand Each Coat

• Allow each coat the sufficient amount of time to dry, according to the manufacturer's instructions, and sand each coat before you apply the next coat. Sand away any bumps and ridges. Use fine-grit sandpaper, which has a higher grit number. Use at least a 120- or 150-grit sandpaper, although some professionals advise to use a 220-grit sandpaper, which is even finer and creates an even smoother surface. Wear a dust mask and also goggles to protect yourself while sanding.
  
  

Divide an Entire Wall

• If you are skim coating an entire wall, as opposed to one area of it, start from the where the wall meets the ceiling and work down to a midway point on the wall. Initially apply the mud with horizontal strokes, and immediately smooth the mud surface, removing any excess, with vertical strokes. Start at the wall baseboard, and apply the mud upwards to slightly overlap the mud already applied at the wall's midsection. Work across the entire wall using this method.