What I am confused about is that I can prune this a number of ways.
1/ Leaving one side branch per whorl and create an alternating pattern.
2/ I can cut it all harder back and prune to 2’s. Eg. 2 divides to 4 divides to 8 etc.
Maybe overthinking this but is there a rule per conifers/pines to us Rule 2.? And as CB per the picture, can I cut half of this foliage off?
Aren't both these options effectively the same thing? Leaving one branch at each junction is effectively pruning to 2s?
2x2 branching is just as important in conifers as deciduous. Try to develop 2x2 branching wherever possible.
Just to be clear I have no spruces in my collection so can't offer first hand experience here. Having said that I would try cutting off up to half the foliage on any species, including blue spruce, but I'd also take note of the warning given by
@Cofga
Pruning is good to promote growth and ramification but some species take longer to respond than others. Unfortunately moderate pruning often does not give the same response as harder pruning. Lower branches also respond with less vigour and take longer to shoot and grow when there are dominant branches above.
Looking closer at the photo I think you will have to bite the bullet soon. That branch is getting long and end heavy so you do really need to get more growth further back to create balance in the whole tree. Removing as much longer, end shoots as you are comfortable with will be a good start.