The regular clothes iron is fine but when the guy told you to hold it above the film he obviously didn't say how high. You, also obviously, took "over" to refer to about a foot so you could see what was going on.... Just kidding...
But the iron DOES have to be almost on or even in light contact with the film for enough heat to hit it and reach the shrink point temperature. That's why your covered hanky iron method worked.
And as you found out it's important to keep the iron away from the edges or the colour/glue layer will remelt and you'll see it shrink away from the edges.
Also I've found that Solarfilm (yes we get that here in Canada too) is very soft and has almost zero torsional stiffness. It's far from my first choice for covering open bay wings like you GL. In a dive it could very easilly go into a flutter that covering with a stronger film like Monokote would prevent. Solarfilm, on the other hand, works super well as a trim film. The very low adhesion temperature all but eleminates air bubbles. And the very low adhesion temp prevents the Monokote from being reactivated in any way.
Good luck with your new model.