Rooting hormone is pretty useless when used on roots, despite what you hear around bonsai boards.
Rooting hormone acts as a switch for NON-ROOT tissue to produce roots. In other words, it won't really stimulate root tissue on root tissue, since root tissue is already root tissue. Rooting hormone can actually slow down rooting when placed on roots. It is meant to stimulate roots on trunks and branches.
FWIW, I would avoid trying to air layer any of the species you've listed unless you run across some very interesting twisted old branches. You can usually do better just buying a $15 sapling at a nursery and chopping it or planting it out for a while. The results are more reliable and you've got more going at the beginning with a larger plant with a set of roots already in place.
Trunk chops can be done just before bud burst in the spring. Root reduction can trunk chops can be done at the same time, but alternating a trunk chop one year, then reducing the roots the next can be a little easier on the tree. Fruit trees are quite vigorous (unless you're dealing with a specialist grafted variety--avoid those).
Be warned, fruit species are notorious for attracting bugs--all kinds of them.