Try lollipoping or cleaning out the smaller growths on the branches first and third week in flower. This will encourage the growth in the top colas minimizing popcorn buds. I generally leave 6-8 nodes per branch except the main stalk. The more even you can keep your canopy the more light efficient your grow becomes. Depending on the strain, I usually bend my tops to encourage the branches to catch up. Bushy results, I'm telln ya.