I do basically the same. I've also switched from more expensive and complex video editors to camtasia 9 to speed up the editing process. What wears the most is the time lost waiting for rendering! Breakes the work flow! I always record the course and then I'll edit at the end. Sometimes I add one class or another when I see the material ready, for polishing What works for me is to create a video file with the introduction ando other for the "background" parts like text, images, quots etc.
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