when learning an instrument half the battle of improvement is just becoming aware of a weakness. i mean, the other half is the part where you do something about it which is the actual work part, but first you have to identify that there is a weakness in the first place. becoming aware of a thing can be difficult, though, especially if you've been playing for a long time. every time you pick up the bass there are habits and tastes that have been baked into the process that those weaknesses have been normalized and therefor invisible.
well, okay, you noticed something about your playing is trash... uf! that sucks, but the good news is you want to fix it, and that's cool. but what now? well now is when you have to figure out some exercises to turn that weakness into a strength... or at least bring it up to speed. this can be tricky. youtube is probably the first place people go for this sort of thing and there might be a video addressing it. but i would venture to say, if there is it's probably not terribly helpful. since learning an instrument is 99% a self-taught endeavor you are the most qualified person to address your own needs.
being able to develop your own exercises is crucial for your own development. exercises don't have to be a life-long thing that you do everyday. they don't have to be complicated or lengthy. in fact, the easier and shorter they are is probably better. an exercise can be a one-off to help you work out a difficult riff, or some challenging rhythm in a piece. once you learn that one specific riff you toss the exercise and move on to something else.
i personally will usually break the problem down into the smallest piece i can think of. that way i'm really only working on one aspect of the problem at a time rather than multiple issues. for example, i've recently been working on my string muting with my right hand. i'm trying to dial in muting with my thumb as i move across the strings. i have a bad habit of just anchoring my thumb on the pickup (see the ThumbThing™) so i'm trying to focus on anchoring my thumb on the strings. i was doing some scales where i didn't have to think about what i was playing but could just watch my right hand. i wasn't trying to incorporate this while trying to learn a new song or while working on arpeggios, etc. the simplest thing i could think of that would require me moving across strings consistently was a major scale which would leave 100% of my focus on my right hand.
doing that for a short while i started working it into songs from my repertoire. this was tricky because some of these songs i've been playing for years in a particular way so i really have to fight muscle memory. having done the exercise with the scales, the technique was worked it into my right hand enough that applying it to songs was much easier. and yes, there have been some parts in songs that have required me to make a quick exercise to deal with overcoming muscle memory. sometimes it takes a few minutes, others a bit longer. but once i've overwritten that muscle memory i can toss the exercise and move on.
this sort of thing obviously transcends bass. it's a skill in an of itself and it applies to pretty much everything you want to learn. the more you do it the better you get at it.
