Here's what a fellow member says...
"2tbs a gallon, once a week, is the reccomended dosage, so I would just stick to that. Also only use it during flowering, or if you really are eager to use it, a week before flowering. It really has no affect during vegging, and might attract ants. Using to much molasses, will attract some unwanted pests, so dont over due it. If you do 2tbs a week during flowering, you should be fine. And you can use the molasses right up until harvest, so dont worry about flushing it."
& that's the dosage i use. usually i split it like 1tbs a gallon twice a week...