I'm looking for suggestions on how to do this with the minimum shock to the tree. I know the best suggestion is to transplant prior to this happening, but for a variety of reasons I could not get to this until now. And the compaction of this soil happened quite fast, over the last month or two; surprising how quickly it changed from when I first noticed some slowing of drainage.

From other posts, it seems the best procedure would be to place the tree's root ball with current soil into a vat of water for a while, and then carefully remove the old soil with minimal damage to the roots. Any other/better ways to do this part?

I am intending to use CHC 4:1 with peat mix for the new soil medium. Pot will be a plastic, non-porous one. I did have some concerns about using a CHC based mix with a non-porous pot material. Will the CHC hold their moisture too long in this sort of pot?

Would some minor pruning after the transplant be advised to better balance the leaves/roots?

And I plan on keeping the tree out of the sun for a couple weeks after the transplant.

Anything else?

FWIW, the tree is about 3' tall and wide, in a 16" pot.

About potting mix I have been using 50/50 pine bark mulch with peat moss and mix in some soil conditioner. But there are so many potting soil out there. Also from my experience from repotting all of my trees. When I first started I used some native soil with some bark. So I repotted all of them because like you all my plants were experiencing compaction. What I did is I got a big container full of water and dipped it in the water and sloshes it around in there till I got most soil out. I didn't remove it all but most of it, don't worry about getting it all because most times you will do more harm than good. Also straighten up any roots that are tangled with gentle care.
Good luck and feel free to ask more questions. There are alot of people that can chime in with more opinions n

Steve, it is not the amount of water, or the length of time the moisture remains in the root zone that causes the problem. It is the loss of root zone oxygen that causes the problem. Open growth mediums such as bark or CHC mixes retain good root aeration, even with heavy watering. As David cautioned, you do not need to remove 100 percent of the old medium. Remove as much as possible to the point that you are not causing root damage. Millet (690-)