Generally, plucking is an indication that you are creeping. If that is the case, working on plucking is frustrating because you are working on a symptom and not a cause. If you could video yourself with a fairly closeup shot of your drawing hand, and play it back in slow motion, you would know if you are creeping or not. If you are creeping, you can solve that problem and probably the plucking will be solved along with it.
It is possible that you're plucking for some other reason, but I would want to eliminate creeping before I went any further.