If I want to work on a certain aspect of my playing, I try to learn an actual piece of music that’ll help.
E.g., if I want my playing to be more rhythmic, I’ll learn some rhythmic music, rather than practising rhythmic permutations. That’s my first port of call. If I’m still not satisfied, I’ll try something else; maybe that’ll be maths and thinking, but you get the idea.
Music first; exercises last :)
Anyhow, if you want to work on your picking, I suggest you learn this:
Villa-Lobos Etude No.1
It’s an actual piece of music!
If you pick it (alternate or hybrid), then it offers many challenges: string crossing, outside-picking (if you start on a downstroke), inside picking (if you start on an upstroke), stamina, it’s been played by every classical guitarist so there are many ways to hear it played, and so on.
But, I think the biggest challenge with this piece is that if you play it metronomically, then it’s an awful piece of music!
So the challenge is how to be expressive with it – how to turn that tedious descending diminished section into something worth listening to.
If you play it like a robot, then it’s just teeth-grindingly absurd.
And yet, there are gazillions of versions of it everywhere.
Every classical guitarist knows it. So figure out how they make it sound good.
Same thing with Flight of the Bumble-Bee.
Don’t play it to a metronome.
Listen to this and try to be that expressive with it.
Feel free to add your additions to this (at present) two-page book of technical challenges. In particular, how to approach a certain piece? what challenges lie waiting? … … …