Sorry it took me a week to answer, Bob.

Maybe I'm getting ahead of myself. The tree has been doing so well that I thought maybe I could start actively encouraging backbudding a little, while still keeping my main focus on promoting health and vigor.

Maybe we need a "Janus" smiley -- the Roman god with two faces on opposite sides of his head, who carried a contradiction within himself!

Cut the old needles off, it helps to control fungal infections and opens up the tree, do not cut the buds off of the ends of this tree. Let the tree grow and gather some strength. If you want to cut off the terminal buds to encourage back budding, then I would start fertilizing in the spring as soon as the tree "brightens up" and starts to move. Then in mid-late May or so, do your pruning and then keep the fertilizer on the tree and let it pop. Larry Jackel discusses this in his book, I have done it as well. In my experience we have done better by cutting needles in the spring, fertilizing and placing in full sun.  John