i got 2 plants (@4.5wk veg from seedling) atm that i topped using uncleben's method (stickied at the top of this forum), then when they had grown for a few days and i had 4 main branches, i tied them down below gradually untill the tips were no longer the highest point of each branch, LST style, causing accelerated side growth, and shorter internodal space too i'm sure..
well, 1 of them is in a 30l pot now, and the other will be xplanted from 15l-30l pot asap, and what i have now are two low, bushy beauties with a whole heap of growing tips and an even canopy - it doesnt take much work to adjust the ties either.. delaying flowering (i reckon i still need another week or so veg) is agony tho.
now i'm only on my 2nd grow and havent topped before, but be carefull - i have 2 other plants that i topped a little earlier than advised - this shocked the plants a little much and i musta lost about a week of growth.. they're fine now, but i cant help thinking that if i'd waited then they'd be substantially bigger by now.
for training, search "delta9's low stress training/LST" or similar btw
hope this helps