Exactly like Bill said. The idea is to get the smaller feeder roots growing closer to the trunk. Now under the ground all you have is the largest roots, only keeping the tree supported. The idea is to "chase" the feeder roots toward the trunk to allow for putting in a finished pot. If you can work the tree in the ground then i think it should be quicker. There are not alot more seasons to repair any scars, or recover from any transplanting. The first year in the ground, or in a training container usually is just getting used to its new home, then the second year you start getting lots of growth. I may be wrong, but if your trunk is at the point you like, then go ahead and start pruning, and keep any branches you would use to heal any wounds, or any branches used to thicken any more areas. I would definately check into it more. This is only my second year, but have many in general landscaping. I have a couple trees native, and still in the ground that i have daily access to, and they dont seem to be phased by any pruning on the roots, or the top. I do any major cuts when dormant before any buds start to push. Then i let them go until mid summer when i do some more. I am keeping the branches pruned to two nodes. Just do your work at different times. Good luck.