Gohan's shield is a sad thing indeed. If I don't feel like detonating a beam in front of it or behind it, I'll just throw a kamehameha or a few generic beams into it. When he drops it to fire, I just swoop in and knock him out of the air. I have only failed at doing this once.
Remember that the more damage you do to the shield, the longer it takes to fire.
Oh, the other thing I like to do is to wedge myself between someone's shield and a wall and just stare them down. Their ki drains away as it tries to push you out, but being inside of the shield you can even get away with a few ki blasts. Albiet you get hurt as well, but you can start up a blob and leave.