Spruce are always a long term project tree, there is no such thing as "Instant Spruce Bonsai". If you look at the $5 Box Store Spruce Challenge thread, where many bought sale priced spruce intended as Christmas decorations, you will see all manner of wild chop, prune, wire & repot all done on a cold day in December or January, and if you check the 2016 or 2017 contests, near 100% of these are dead a year later.
The ones that survive, are the ones that people took it slow, and paid attention to the "do the correct technique in the correct season". Those will have survived. Spruce are not absolutely "one insult per year", you can "sometimes" do more, but it is a great mantra to "slow your roll" if you are fighting the impulse to do too much, too quickly.
Spruce require time to recover from root work, there is no getting around this. I picked up a blue spruce (P. pungens) from a nursery going out of business. It had been in its 5 gallon nursery pot for 10, maybe as much as 20 years, totally root bound. The first thing I did was repot it. I removed between 50% and 75 % of the root system. I removed at most 15% of the foliage. It took 3 full growing seasons before it recovered enough to be ready to take the next step and do the first styling. There is no rule, that give it a season and it will be ready for the next step. They take the time they take. Before you do anything, look at the tree in front of you, ask yourself "Is it healthy enough to survive what I want to do now?" and "Is it the right time of year for what I want to do?" If the answer is "No" to either question, "Back away from that tree, give it more time."
I'm largely in agreement with
@Wires_Guy_wires - in that if it were mine I would work the roots first, then worry about styling later. One or two or even more years later for the styling. Health of the tree determines everything. Most "off the shelf" bonsai pots are 4 inches or less in depth, they may be quite wide, but the depth will be shallow. When you do your root work, attempt to get the root system shallow enough to fit in a container 4 inches or less deep. I like Anderson flats, heavy black plastic 16 x 16 x 5 inches with mesh bottoms as my grow out containers. They hold roughly 3 gallons (nursery trade gallons) of potting media, and will work well for growing out stock in training.
I do most of my repotting of conifers between July 15 and August 30. It works well for my zone 5b climate, but my summers are relatively mild. I have done late winter, early spring repots, and for spruce they worked well enough. I personally have many demands on my time in spring, late summer has always been easier, due to more free time.
