Strip The Steel Door and Frame

• Remove all hardware. Detach all the locking hardware and strike (kick) plates from the door. The equipment can easily get paint stuck behind it or within its locking mechanisms, which can cause malfunctions.
  
  Remove any weather stripping from the door frame by simply pulling it away from its groove in the door frame. If the weather stripping is not able to be removed, a strip of masking tape may be used to cover the area to keep it free of paint.
  
  Clean the steel door by rubbing a washcloth soaked in denatured alcohol all over it. This will remove any surface contaminates that may affect drying and how the paint sits on the door. Once the door is clean and dried, apply masking tape to any glass areas of the door.
  
  

Sand and Prime The Door

• Remove the door from its hinges. Lay the steel door on two sawhorses to keep the surface level and avoid placing the door directly on the ground. Examine the door for deep scratches or dents along its surface. Sand any of these scratches or divots using 80- to 100-grit sandpaper to assist with the adhesion process.
  
  Apply a coating of auto body filler to the sanded scratches and dents, allowing it to try completely before going back and sanding the surfaces level once more. To re-sand the surfaces begin with 100-grit sandpaper then move up to a 150 and finish with a 220 sandpaper. Finer and finer grades of paper will ensure the surface is smooth and level.
  
  Spray the door's surface using an aerosol primer. One to two coats will be sufficient to ensure the subsequent coats of paint will adhere to the steel door. Remember to avoid spraying the holes where the door knob and hinges are placed too heavily as it may alter the way the door fits in the frame.
  
  

Painting the Steel Door

• Use 100 percent acrylic paint when working with a steel door. Acrylic outlasts oil-based paints when used on steel, since the oil only sits on top of the steel whereas a wooden door allows the paint to soak in. Paint sprayers will create the smoothest finish for the door and use the least amount of time to finish the job. Apply two coats of finish to the door, allowing it to dry completely before replacing the lock, removing the masking tape from glass/weather-stripping and returning the door to its hinges.