I'm not sure, you would need to look at things in this thread that might be relevant and discard the rest...?
Obviously no need to bend trunks initially. Pines do a very good job of growing straight on their own which is what you'll be looking for in a formal upright.
As for stem cutting etc ... I would perform this to get maximum branching down low. Whether you use that in the final design is debatable but would provide an abundance of sacrifice options near the base to help with taper which is a big component of a formal styled tree. It also helps with the nebari (IMO) which is also important in any pine bonsai really.
It's not often you see a formal upright shohin sized pine (at least where I am) and I've never attempted one. It feels like a style for a bigger tree so out of the scope of the competition really. I think the techniques to balance energy and encourage growth etc are still relevant but perhaps not exactly "as read" in this thread. You might need to tweak timing etc...
Would I ground grow a few to see what happens ...? Yep.