I find that whenever I get the smash ball I have a difficult time targeting any one person and completely hunting them down to death, yet CPUs or Amiibos do it so simply and I have no idea how.
Usually, if I get the smash ball, I try not to move up or down so much and instead cover the ground of the stage(I play Omega/FD alot) or go after a group. It's easier to knock opponents around than to try and go after one particular person.
If you're doing a 1v1 and the smashball is out, I don't really know. Maybe trying to push them offstage and keep them off is better than dragging them off.
It's hard to do it precisely and I haven't seen anyone (besides CPUs/FPs) work with his final smash like that. XD
Tactical ideas aside, moving in small taps as opposed to holding in one direction on the joystick helps you make more precise movement. (probably slower, though)
Pressing the A to release the thunder makes him move around more spasmodically, so if you're looking to aim precisely don't press the button. (Good for sending others flying, though, if you're looking for a kill)
I'm no expert with his smash (I usually play with no items) but that's just a little tidbit of "advice" I have to give. You'll probably get better suggestions from someone else, but I figured I would throw in some ideas. :3
