Number your ideas. But numbered lists create goals to motivate participants. Also, lists provide a reference point if you want to jump back and forth between ideas. Build and jump. The best facilitators nurture the conversation in its early stages, step out of the way as the ideas start to flow, and then jump in again when energy starts to peter out.
Fluency is a very rapid flow of ideas, so there's never more than a moment of silence.
Flexibility is approaching the same idea from different viewpoints. Make the space remember. Good facilitators should also write ideas down on an accessible surface. Ideo used to hold its brainstorms in rooms wallpapered with whiteboards or butcher paper. Stretch your mental muscles.