Ask him if he knows what brand/kind of epoxy he did the heatgun trick to. If he's actually done it then no doubt it'll work for you if you've got the same gun and used the same epoxy BUT..... I wouldn't come close to trying it on just any epoxy with any heatgun, especially since the depth of the joint would work against the heat getting deep enough into the epoxy to "melt" any past the surface stuff.

About the only solution to a badly aligned wing joint, no matter what glue was used, is THE SAW !!!

But truth is, once you get your mind to accept the job, it ain't too bad a job, if you're careful.