I do a lot more work with glass cloth & paint than film coverings but the metallics do seem to act differently when I've tried them. I've not heard of using hairspray before using iron on covering. Anyway, hope the model turns out well, post some photos when its done; Banshee is neat airplane.

The only modeling use I recall for hairspray is to spray balsa sheeting used for sheeting a foam wing with hairspray prior to applying expoxy for skinning the wing. The theory was the hairspray prevented excess epoxy from soaking into the wood so less would be used, and create a lighter wing panel. This was from the days of 800 sq in pattern models with 10cc 2 strokes where every gram saved (in theory) counted.