While molasses has it's uses in flower, the reason you're going for is a popular misconception. Molasses does provide potassium, which aids flower production, but not a whole lot.
The reason you do use molasses in flower is all about the root and microbes relationship. The plant makes it's own sugars, any extra sugar not used in plant growth is exudited thru the roots where it feeds the microbes. During heavy production periods(flower) however, sometimes there's just not enough sugar left for the microherd. So feeding molasses ensures they stay alive and well populated, doing their part to ensure the break down of matter and uptake of plant nutrients...leading to bigger, more potent buds (strain pending).
You gotta be careful though, the microbes are like diabetic destined children, they love sugar. Too much molasses and they'll only be chowing down on that instead of the organic matter in your soil.
I reccomend applying 1/2 a tbsp a gallon every other week, maybe every 9 days at the soonest. Once you hit you last week or two I would cut it, unless you're doing no til. Rules are probably different then but I'm just getting into that world. Someone else would have to chime in for that angle.