My first thought was a strong light if current light isn't producing dense buds. Training the plant helps create a better bud. MIMEDGROWER actually mentioned in another post that with tomato plants, if you train them, they become stronger and create a bigger fruit.
I did something to one of the colas and now it created three bud sites that are close to one another. Once they fill in, that will be a big dense bud.
Look, this is what I mean. I only have it under a 400W and I try to go moderate with the nutes. I thought about bud hardeners but then I said to myself, let me figure out how to grow the best plant and then once I find the 'recipe', I can start tweaking it so I have a base to refer back to.
For that training, I topped, then let the nodes form a few levels. Then when it got pretty wide, I found the furthest shoot and cut every single leaf in the bunch on the same line. So when they grew, it created this nice three bud site that is going to be pretty dense when it fills in (i hope :P)