Having done this a multitude of times, I can tell you this method will not work in warmer climates. The foil does not sufficiently prevent moisture loss in the growing media. I always seal my layer in plastic before putting the foil on to prevent it from drying out.

This was wrapped in the plastic bag the grocery store circulars used to be mailed in. Since it was covered with foil, I wasn't worried about using a UV resistant plastic, and the thinner plastic seals better. The ends are sealed with electrical tape. Since the tape has some give, it can be stretched tight around the ends for a good seal.
As Martin noted, a girdle is not necessary for an airlayer. However, if you want to girdle the limb but do not like the idea of the knife work, a veggie peeler is a great alternative. Use two hands when doing this (again this is from experience) with the thumb from one hand as a stopper for the hand peeling back the bark. It is easy to take too much off. Also, I place my girdles at the bottom of the layer. When the offspring is removed from the parent, I cut the girdled portion off.
~james