From DIYinfo.org
Always open a door before you paint it. Leave the door frame until last; that way, any splashes of paint that get on the frame as you paint the door will not matter as you will cover them later.
[edit] Flush Doors
1. With a 3in (75mm) brush, work from the top down in horizontal strips, moving about 600mm at a time. Work to wet edges, if the paint dries, you will get a paint line which is very difficult to lose.
2. As the brush empties, cross-brush to even out the paint.
3. When a width is complete, brush downwards over the painted area, leaving a wet edge for the next strip to blend into.
[edit] Pannelled Doors
1. Work in the sequence illustrated for best results.
2. Use a brush of a suitable size to paint each part of the door, a smaller one for the mouldings than for the panels, for instance.
Warning: Do not overload the mouldings with paint; this is a common cause of drips and runs.
[edit] Glass Pannelled Doors
1. Use a paint shield (above), an angled cutting in brush or masking tape to keep paint off the glass. Whichever you use, allow paint to go onto about 3mm of the glass to seal where the glass and frames meet.
2. Paint the rest of the door with a 3in (75mm) brush.
3. If gloss paint accidentally goes on the glass, remove it with a rag damped with turps before it dries. Remove emulsion paint with water.
If paint dries on the glass, scrape it off with a razor blade.
A scraping tool with replaceable blades can be bought for the purpose.
[edit] Using Two Colours
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Fig A: If the door is painted a different colour on each side, paint the lock edge the same colour as the side of the door which opens into the room.
Fig B: Paint the hinge edge of the door so that it is the same colour as the adjacent, visible face of the door.
Fig C: If the door frame is also painted a different colour on each side, all the parts which can be seen from one side when the door is open should be painted the same colour. Paint the door jamb (the side of the door frame) in the same colour as the frame in the room which the door opens into.
It is generally thought unnecessary to paint the top and bottom edges of a door. However, in humid conditions, doors absorb water through unpainted surfaces: this causes the door to swell and bind against the jambs, so protective paint is advisable. Also, if the top of a door can be seen, for example, from an upper floor it would look better if painted.
