I don't try and go too in-depth these days, does vertical mulching, radial trenching and soil decompacting with the terra tree/ terravent work and show significant results in stressed trees, yes and that's really all I'm concerned with!
Would I decompact and turn over an entire root zone with an Air-Spade NO WAY some do I don't, soil de-compaction IMO is best carried out in moderation. From my own experience the Air-Spade will very rarely physically sever fine roots, but I do believe it will dehydrate fine feeder roots. That's why I don't de-compact any more than 20% of a root zone/compacted area [with Air-Spade] The short term damage in my experience is far outweighed by the long term benefits of de-compaction. Feeder roots grow quickly IMO after de-compaction, hence the positive results.
My preferred methods of soil de-compaction these days are vertical mulching or de-compacting with the Terra Tree and mulching the root zone afterwards. If incorporating mulch isn't an option, I like to use soil conditioners/bio stimulants and compost teas, I rarely if ever use inorganic fertiliser or mycorrhizal inoculants these days, because with fertilisers we don't know the true effects long term. I have however in the past used weak fertiliser dilutions that have proved beneficial all be it short term so far! and as for mycorrhizae, I had a long chat with a mycologist some months ago, he specialises in mycorrhizae, and he like me is convinced trying to add off the shelf mycorr potions to mature trees is a waste of time, far better to try and make ideal conditions for the myccor that's present.
Anyway lets not forget the Air-Spade has many more uses than just de-compaction, I use it as a excavator for root pruning, inspection pits, root investigation etc etc. As for training, who has enough experience to put together a training package? I learn something new every time I use the Air-Spade.
If a training package is put together and no doubt somebody will, it will be a H&S money extracting jobby, IE do not point and blast your colleague wth Air-Spade, do not use Air-Spade under influence of 10 pints of Stella a spliff or after injecting smack, do not use Air-Spade for pest control purposes and blast bunnies and rats out of burrows, such training I'll pass up on..