I've tried a few ways to air layer. The one I find most success in is soaking the sphagnum moss in the water for about 30 mins, wound the spot about an inch, rub rooting hormone or honey on, use a plastic bag to wrap the sphagnum moss around it, make sure to squeeze as much water off as you can, use black electric tape to seal both top and bottom from letting water in, seal the vertical line of the plastic bag as you close it, then use foil paper to wrap it again one more time to tighten everything.
Other things to keep in mind are the time of year (preferably summer with strong heat) and branch out in the sun instead of inside the canopy. I've been able to do quava, plum, wax Jambu, lemon, orange, and cherimoya with this method. I normally give it 3 months for the weather here in San Diego. Good luck.