plants are not going to take in molasses through their leaves; you'll just get them all gummy and nasty and possibly clog the stomata= bad idea.
use molasses whenever you feel like pretty much. I give it once a week all the way through flower, about a tbsp or so per gallon.

foliar feeding is for correcting deficiencies without overloading the soil most of the time. like if you are locked out but shitty soil conditions, the plant may benefit from a foliar feed with like spray-n-grow for example, depending on your def symptoms.