This guide will show you how easy it
is to paint an interior door. Just follow these 8 easy steps and
you will have a beautiful interior white door.
You will need the following for the
job: 
- Medium Sandpaper
- Fine Sandpaper
- Wood Primer
- Finishcoat
- Paintbrush
- Cotton Cloth
- Dust Sheet
- Masking Tape
- Screwdriver
- Sugar Soap
- A Door Stop
- Dust Mask
Step 1 - Prepare the Area
The most important thing before you start is to ensure your area
is well prepared. You should make sure to wedge your door so it
doesn't move during painting. Push back your door until it is
firmly wedged. Put down a dust sheet under where you're going to be
painting to avoid damaging the floor. If possible remove the door
handle. If not, cover with masking tape to avoid damaging it with
paint. Make sure you have plenty of space to work, and that the
area is well ventilated. Doors that have been previously painted or
varnished, should be washed down with sugar soap. If it is a raw
door you can go straight into sanding it. Don't forget to put on
your dust mask. If the door is in poor condition, the paint must be
stripped back to the bare wood.
Step 2 - Sanding Down
Begin by sanding down the door using the medium grit sandpaper
or sponge. This will remove any blemishes or dirt on the wood and
will help the primer to stick to the door, and give a better
finish. When sanding wood, always sand in the direction of the
grain. Be sure to wipe away any dust off the door before painting.

Step 3 - Using the Right Primer
If you're going to use a water based paint use a water based
primer, and if you're going to use an oil based paint use an oil
based primer. Don't forget to give your tin a good shake before you
start. Now you're ready to start priming your door. Remember to
follow the same steps whether you're priming or painting.
Step 4 - Priming the Door
Paint in the direction of the grain using even strokes. Make
sure to get yourself a good quality 2 or 2 ½" paint brush which won't shed its hairs.
Follow the same order of work whatever you're painting or staining.
When painting interior doors, paint
any mouldings first, then the panels, then the central verticals
and horizontals, then the top and bottom horizontals. Remember to
paint the rim of the door to match the room the door opens into to
blend with the decor.
Step 5 - Sanding the Door
When the door is dry you can gently sand it with a fine
sandpaper or sponge. This will ensure a nice surface under the
paint. Once you have finished your fine sanding, make sure to dust
off your door thoroughly.
Step 6 - Painting Preparation
Now that you've finished sanding the door, you can start
painting. If you use a one-coat finish paint, you won't have to use
undercoat. Some people might prefer to use a gloss finish, it
doesn't make any difference. Whatever paint you decide to use, make
sure to read the tin. Brush on your first coat of paint. The same
method applies to the finish coat as it did for the primer.
Step 7 - Painting the Door
Lay the paint on by making two or three separate downward
strokes. Without reloading the brush, fill in by cross brushing.
Still without reloading the brush lay off with light even strokes
and smooth out with a light upward stroke. By not overloading your
brush, you reduce the risk of runs and drips and it gives you a far
better finish. You should leave it to dry over night. 
It's a good idea between coats to wrap your brush in tin foil or
cling film, to stop it drying out between coats.
Step 8 - Finishing Touches
Now that your door is dry, all you have to do is replace the
handle and remove the dust sheet.
Sometimes you may need to apply another coat of paint. If this
happens, gently sand the door down, clean off all the dust before
applying the other coat and follow the steps in this guide.
Article submitted by Adam Gibson