I lollipop and defoliate about a week or so before i flip to 12/12.
After that, its simply a matter of maintenance as far as lollipopping goes. As the plant stretches and grows, it will produce new growth/bud sites on that bottom 1/3 of the plant that i cleared previously, but i try to remove it as quickly as possible, to prevent wasted energy or major stress during flower.
I defoliate again around week 2-3 of flower, while simply continuing to maintain the bottom 1/3 of the plant to keep it barren of new growth. The lack of growth on the bottom 1/3 allows energy to be concentrated on the upper 2/3, as well as allowing better air circulation from under the plant. And then defoliating allows more light into bud sites that would otherwise not receive any, as well as better air circulation. Plus defoliating seems to produce denser buds in my experience, and saves a ton of time when trimming after harvest