I was fortunate enough to have a lesson with Oscar Herrero last fall and he walked me through a series of warm up routines that he says he spends an hour on each day. These are very methodical and I think you have to have a certain kind-of Zen attitude towards them. I'm striving to spend that amount of time with them, but I do at least 15min - 20min each day. I'll try to walk you through an example just with pulgar, and you can extrapolate to other techniques.
First, each exercise is played with 4 beats, then 3, 2, and finally 1 beat. Ex 1: Open Strings starting on the 6th string - 4 beats (paying attention to your technique at a slow speed), 3 beats, etc. Then the 5th string, 4th, etc.
Ex2: begin to incorporate the left hand using all combinations of fingerings per each new exercise, eg. (4 beats per finger): 1rst fret, index, 2nd fret, middle, 3rd fret, ring, fourth fret, pinky. Then vary, say (for example: 1, 3, 2, 4). There are lots of combinations! Then do the same thing walking up and down the strings. Think of your own variations (1 beat sixth, 1 beat 5th, etc). The point is to pay attention to your thumb technique the entire time. There are lots more, but I'll only mention one and you can figure out others: String Skipping. Example: 4 beats 6th, 4 beats 5th, 4 beats 6th, 4 beats 4th, etc.
You can do similar exercises for picado, and arpeggios, with appropriate modification. Even more complex techniques, such as alzapua can be done this way.
Mind you, I am aspiring to have the concentration and patience to do these myself, so take this for what it's worth. However, Oscar is a wonderful player and teacher (as is Kai, so hopefully he'll weigh in) and my personal teacher was a student of Oscar's for 10 years or so and did all of these and has pretty flawless technique, so there's evidence that this works! Cheers -Paul