RE: Is a Heat Gun really needed ?
I use one. I generally tack down the perameter with the iron then do a first light pass with the heat gun just to get the wrikles out. I pretty much use the heat gun always on the wing tips, pull and stretch. Cut off the remaining and the trim iron finishes it smooth. It pretty much goes faster doing the general area shrinking on the wings, fuse, stab, and fin. Then I go over the wood contact areas with the iron again. Works for me. Others probably have different ways.
Edwin