lollipop in the first week of flowering? or would I do too late?

Its up to you when you do it, some people say doesn't matter, some say week 2 or later. I will usually wait until the stretch is done. I find that any heavy defoliation/high stress training will stunt growth for a few days. If you do it mid stretch it may be detrimental to your overall plant growth/yield. I would wait until they have stopped the rapid growth phase at the start of flower (stretch) then defoliate fan leaves and strip lower branches and bud sites that are not getting much light, they will end up being fluffy popcorn that will be a pain in the butt to trim or will just end up in the hash/edible/trim pile.