Never used a shrinking disk but I know a lot of guys swear by them. I'm sure that now that you've brought up the subject you'll get lots of conflicting opinions.
The torch method has been around forever, works very well, especially in a case like ours and doesn't require buying yet another tool... assuming you have an oxy/acetylene torch which is kind of a basic requirement if you're rebuilding an old vehicle.
Oddly enough, I was unable to find the torch method using a hammer and dolly on U-Tube but there are a few that do not use a dolly. I tried without a dolly and got no appreciable change.
There's also a reprint of an old auto body instruction book that describes the method very simply. Too bad you're not closer I'd like to have another crack at it on the back of a cab.
EDIT: The name of the book is Metal Bumping by Frank Sargent
Last edited by Czechman; 04/29/2010 12:43 PM. Reason: Added book info