A light spray with a spray bottle is all that is needed, and only on one surface will suffice. Spread the glue as thin as you can with a Bondo spreader or something similar. It is amayzing how little of this glue will achieve an absolutley aggresive hold. Position the skins and weight it down with the core huls. Or better still vacuum bag it until it cures. You will never go back to 3M #77 (I never liked it) for sheeting wings.

Vince