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