I use SuperThrive in every watering, from start to finish.

I use Schultz Cactus Juice (1-7-6) about two weeks after switching to 12/12. Since you'll repot and be adding new, good soil to the larger pot, your plant will draw plenty of nutes out of the new soil for those first two weeks of flowering.

And, yes, just plain water (with SuperThrive) for the last two weeks.

Just my way of doing it from HD's suggestions...