Shrinking Disc Demonstration
In the video I demonstrate using a shrinking disc, by removing two dents in a
domed panel.  Once I got the dents shrunk back down (I did NOT use a hammer
and dolly, only the shrinking disc for demonstration purposes), I ran an DA air
sander over the panel to show exactly how smooth of a finish can be achieved.  
You could never tell there used to be dents there.

In normal conditions, you would tap the dents and low areas up with a hammer
and dolly, make a pass with the shrinking disc, and tap up any remaining low
spots before making another pass.  After a few passes your panel with be
smooth, and back to normal surface tension.