Supplements to add to 'promote and hasten growth', the most un-processed sugar, kelp and seaweed extract as Phytokind mention, contain plant hormones which have growth promoting auxins and protects against pathogens. But unlike Phytokind, I also use Superthrive with them, foliar feed with kelp and seaweed extract. Water with Superthrive and Sugar. Stop foliar feeding and using Superthrive durning flowering, as foliar feeding bad for buds and Superthrive is reportedly a Vegetation Hormone. And speaking from personal experience it will make your buds more airy and longer internode distance. So double up on your sugar.

Growing Methods to 'promote and hasten growth', I'm a personal fan of LSTing but not by tieing 90 degrees to the pot or earth, I wait for the plant to get bigger than you would to LST then tieing at around the 2nd or 3rd node from the top and then tieing off at around the 4th or 5th node from the bottom, creating a little 'S' hook type shape. I find that it makes a stronger sturdier plant and promotes the growth of 3 or 4 main branches, (basically Supercropping without the arguement of being harmful to plants). And you get 3 or 4 I've had up to 6 nice 10+" x 3 1/2" dense colas. Then theres also like mention above Supercropping which requires some know how and patiences, your breaking the stalk and stems slightly rotating around the stalk/ stem til you hear a crack, then prune everything off except for the bottom 4 branches. (btw, this steps are backwards, do the pruning step first) then arrange so they all receive the same amount of light and all have good air circulation in between. This don't hasten growth per say well maybe Supercropping, but it for sure will improve your harvest.