Dominick, that sounds like a great method for still-dormant figs. I've only air layered when they're in full leaf, though, so I couldn't slide anything down the branch. I like the clear bottle method because it lets me keep track of root development without disturbing anything (I drape a rag over the bottle to keep it out of direct sun). I've done them with closed bottles (sealed all over with tape) and open (with the top cut off, forming a pot, which has to be watered), and both ways work great. I've only tried the girdling method, but I'm definitely going to try it without damaging the bark just to see how it works. The only fig air layer I've tried that didn't work was a too-thin branch that broke when I girdled it.
I guess the bottom line is, no other propagation method I've tried (except maybe planting pre-rooted suckers) comes close to the success rate of air layering, and nothing else gives you such a large, vigorous plant in such a short time. When I've air layered branches with fruit, the fruit seems to develop even faster, and I end up harvesting it before the figs on the "mother" plant are ready. It's a very easy, forgiving way to propagate figs, and if anybody still hasn't tried it yet, give it a shot!