I'm not very scientific.
I use exactly one blob whenever I remember to during flower...

Seriously add about a teaspoon or so per gallon in addition to your regular fertilizer, whenever you fert during flower. It's not a harsh supplement so you don't have to be exact- def/tox doesn't really come into play.

I have noticed an almost ridiculous difference in my finished product since I started using the stuff.

MAKE SURE IT IS UNSULFURED!!!!!