This might seem intuitive to everyone here, but for me, being a plass player first and foremost, I really just can't wrap my head around this.
I've come to the conclusion that when I'm playing guitar I'm your average rhythm player. I can't solo for **** neither do I have any real interest in it. So I mostly play chords and rhythms and the occasional melody. But one thing I've noticed is that I'm having big trouble playing chords accurately (hear every note clearly), even if it's just basic stuff. I don't think it's my left hand, but rather my strumming technique since I'm not used to playing with picks. In fact, I do a lot better strumming with my thumb and maybe even with my index nail.
So I need practice. But how do I practice this? I know a TON of finger exercises for bass (both left- and right-hand), but none for guitar when it comes to chords and strumming. Any help is appreciated.
For your fretting hand, I'd recommend coming up with some chord drills and working through them at a slow tempo, paying attention to how quickly you can switch from one chord to the next. Do it with a metronome, if possible. Start slow (really slow).
Strumming with a pick is a little difficult to describe in a meaningful way, as it's a tacitly learned skill. The best I can offer is to watch other players, and spend a bit of time working on it. Hold any chord and focus on your strumming hand. Start slow (as always), and try to find a way of holding the pick that:
Is secure without need 10,000kgs of pressure
Allows for accurate playing (I.e, doesn't produce lots of unintended noises)
Fwiw, I'm fucking awful at finger style bass, and I'm back to absolute beginner levels on that instrument. I just get a little practice in each day and it's slowly working.