One of the most common interior painting preparation tasks is drywall repair.
I cannot think of one instance in my 20 years experience of interior painting where there wasn't some drywall repair needed.
Most repairs are simply spackling small holes for hangers used to support pictures or shelving.
Others are larger repairs requiring drywall patches and replacement.
Door handles piercing the drywall, removing mirrors from walls, closing in a door or window, and water damage can all require installing pieces of drywall.
Every interior painted wall has a texture.
The most common textures you will find are smooth, orange peel, and knock down.
I will explain our painting company's technique for each one.
Smooth: This is where the drywall has not had any texturing added.
The drywall is hung; joints are taped, and then floated along with the drywall screws.
The only texture will be from the roller cover used.
This is the simplest texture to emulate and is explained in the following steps;

• Apply the drywall mud to the holes or repaired areas with an appropriate drywall knife.
  
• Sand the patch smooth.
  
• Apply a drywall primer to the patched areas.
  
• Paint the wall by using the appropriate roller cover nap size, usually one-half to three-quarter inch.
  

Orange Peel: Drywall companies use large pumps and spray a drywall mixture onto the walls.
This texture is a little harder to emulate.

• Float the repaired drywall area normally.
  Sand smooth.
  
• Apply a drywall, paint mixture using a three-eights or half-ince inch roller nap.
  The mixture should have a consistency similar to pancake batter.
  Usually 10 parts drywall, one to two parts paint.
  
• Lightly sand the area with 220 or greater grit.
  
• Apply a drywall primer before painting the patched areas.
  

Knockdown: Also known as splatter.
This texture is accomplished by spraying globs of drywall mud onto the walls.
After a period of drying but still moist, the resulting "splatter" is then smoothed with large flat plastic knockdown knife.
Knockdown texture ranges from small and dense to large and sparse.
Emulating this texture can be difficult.

• Float the repaired drywall area normally.
  Sand smooth.
  
• Apply straight drywall mud using rolled up newspaper.
  How tightly you roll the newspaper depends on the texture you are emulating.
  Roll the newspaper tighter for small dense knockdown and loosely for larger.
  You have now emulated the splatter pattern.
  
• After a period of dry time, 10- 20 minutes, lightly smooth over the splatter with a large flat drywall knife, "knockdown".
  First float up, then down, then across.
  If the splatter is dry or cracking, try dipping the knife in water before floating.
  
• Lightly sand the area with 220 or greater grit.
  
• Apply a drywall primer before painting the patched areas.
  

Proper and complete preparation is the key to an excellent Interior house painting project.
All painting contractors realize that the preparation is the hardest and most time consuming part of painting.
The actual painting application is a breeze once the preparation is completed.
This article is written to address drywall texturing, one small area of house painting preparation.