When should I start training and what would be a best technique to use? Any help is great :)

Yes if LST is something you are interested in doing, then now is the time to start! 1st step gently pull her down sideways with some good plant wire be sure not to tie it too tight to the plant itself! As she starts to recover from pulling her down her branches will start growing out as they do pull them down as well and it will be a bit of work because daily you’ll be adjusting your ties! Once you get the branches spread out enough Over a few weeks that’s when I like to let them go back up! Use the LST to shape her body to get optimal light penetration!! Good luck 👍🍀

Depends on what you want to do with it. Plant training is situational. Its a photo so topping at least once with some conservative defoliation will give a bushier plant with lots of colas. Not real sure of the aim so hard to say.

I would say now but are you going to keep this plant in that pot? looks kinda small sized. don't know how others think about this but I would repot before lst.... technique what i do (but i start a bit earlier) is make something hold the bottom. than point the head downward. As soon as it starts picking up again i start to move my fixation clockwise so that it bends the plant and all nodes receive the light...