Spray painting a frame: place the frame in a box, and spray one side of it with your choice of spray paint. Leave it in the sun to dry, and then flip it over and spray the other side. When both sides of the frame are dry, take the frame indoors.
How to Make a DIY Interior Dutch Door : Rooms : Home & Garden Television. Except I'm using the idea to create an interior dog door that's hidden on an existing bedroom door (instead of installing an aesthetically displeasing dog door)