Ok, this question will probably be opinion based, but I try my best to write it, so it can be answered.
My problem: When playing guitar (I am right handed) I lack some speed and coordination in my left hand to do maybe trills (right word? I mean something like this |--5h7p5h7p5h7--|) or vibrato properly. I just can't get my hand to do what I want.
My theory: I compared the ability of both hands to perform certain tasks, like tapping a rhythm and get faster while doing it or moving it in certain ways with a certain speed, and as expected, my left hand wasn't as good at it as the right hand.
The question is not about doing tremolo or trills properly, in theory, I already know that, it's just my left hand, which is not trained enough.
The question is, is it common to do certain exercises for the left hand to increase control or maybe even perform tasks with your left hand you would probably do with your right hand (e.g. learn writing with your left hand)? Are there some well known exercises or (to drill down the opinion based part) any literature describing something like this or is it just a matter of doing excercises for the particular technique to gain better control with the left hand?
Usually, I would ask for your opinion or experience with such exercises, but I know that's not wanted on SE. Decide if this question is too opinion based.