Stewart Robert Hinsley writes

Other features of air-layering, if I recall correctly

1) making a cut in (removing a slice of) the stem.

Or abrading the bark on the underside of the stem.

2) using taped clear polythene to keep in the moisture.

Cling film works well. And I think Dave's drinks bottle would work
equally well.

3) using moss, rather than compost.

The extra weight make cause problems with Dave's proposal.

I agree. I've used coir-based compost, which is a lot lighter than a
soil based one.

--
Kay