Write the 30-second master in self-contained blocks
Repurposing is decided at the scripting stage, not in the edit. Write each beat so it makes sense alone: the demo section should not depend on a joke set up in the hook, and the proof section should re-state the benefit rather than saying 'like I mentioned'. Blocks that stand alone can be lifted into shorter cuts in minutes. Scripts with running callbacks can only be cut by re-recording, which defeats the point.