Except for extremely simple cases, drafting the movie is generally the most difficult and time-consuming part of the process. The general concept is to program and configure PyMOL so that it plays a WYSIWYG (what you see is what you get) draft of the movie that you can use to make design decisions before producing and compressing a movie file.
Depending on the complexity of your movie, PyMOL may be able to play the movie in near-realtime inside the viewer window. In other cases, PyMOL will only be able to provide a rough estimate of what the movie will look like once it is rendered.
Each of the following approaches can be used alone or in combination.