How does one LST a FIMed plant? Where to start specifically?

same as any other LST... before it turns woody/rigid to the point it snapps if oyu try to bend it.. that's too late. apical dominance is what you are manipulating. highest growth node takes the most resousrces. permanently or temporarily bending somethign over to even out canopy is an ongoing maintenance process. what space do you need to fill? what is is responsible for in your tent? etc.. shape it as needed. a larger plant you want to keep things bent down and spreading out until it is wide enough to support the size you want - this saves vertical space too. if it's a smaller plant you may just need to spread out branches as they grow vertically a few inches from each other or more... don't have to be as extreme with the bending in that case, but sitll need something to hold it in place - garden wire or scrog etc. if you understand teh cause and effect of apical dominance, you can shape the plant any way you need to. the only wrong way is one that doesnt fit your needs.