I have used molasses/sugar cane derivatives and am most pleased with them for bulking. I give one time 3 weeks before harvest or I screw up the osmolarity.

Also I am trying some stuff that is mostly K, called Snowstorm Ultra. It seems to help with bulking and with the induced K deficiency I seem to get every round.

I think I pay about 15 a bag and it is 20 mile drive for FFOF, just had price increase so not sure, was $13