He's talking about the System Prefs -> Spotlight -> Privacy (tab)
Adding a folder there, then removing it should only redo the search index for that folder. Not the entire volume. To force-redo the search index for the entire volume, add the volume to the privacy tab. Then remove.
Also, you might need to close Spotlight prefs for a change to take. ie - add folder, close Spotlight prefs. Open Spotlight prefs, remove folder, close prefs.