Hey '55,
No it's a plain ol' smooth hammer and cheapo dolly. Some years ago I too tried without success to shrink some sheet metal on my Pontiac with a propane torch and it scared the heck out of me when I saw a huge bulge form. I gave up and didn't try it again until this Jeep front fender situation.
So recently, I thought I'd research the internet on how to do shrinking with heat. Most everything I found (disregarding the "shrinking discs") use oxy/acetylene for a heat source. Well, I don't have oxy/acetylene and wanted to use propane. Most information was sketchy and incomplete. Many seemed to imply that metal "shrinks" just by heating it up and cooling it down. If that was the case, propane should work like oxy/acetylene, which it doesn't.
After thinking about it, I believe what really is happening with the oxy/acetylene method is when you heat a dime size spot dull red, a small, localized hot bulge forms and you create a large temperature gradient. The hot bulge imparts an expanding force upon the cool, stable surrounding metal. Since the hot metal is weaker, it succumbs to the resistant force and thickens in the bulge area. When the hot spot cools to ambient, the work zone takes up a smaller area...it shrinks!
But, if propane is used for for this passive heating/cooling technique, it takes too long to heat a spot to a dull red, and in the meantime, more heat spreads out far, and your localized "bulge" is so large you aren't going to get the compressive forces from the surrounding cool area; basically the large affected zone absorbs too much of the opposing forces.
Logically however, we can help things along in thickening the bulge by hammering the heated bulge flat. The hammering compresses the large area to thicken the work zone. So it's no longer a passive technique, but it helps things along. The downside of the large work area is having to move the hammer around alot which inevitably creates a dimpled surface. You have to go in after it's cool and fix the texture with more hammer/dolly work and/or slappers.
So that was my theorizing anyway. And it seemed to work for me! Many out there in internet land seemed negative on using propane, so I made the video to show that oil canning can be removed with propane heat.