This question is going to take some time to explain (at least for me), so pardon the length ahead of time. Also note that it seem like it elicits opinions but this is not the intent. I'm interested in people's opinions on what works for them but I'm sure there is an objective perspective based on research in cognitive neuroscience and am aware of some musicians taking advantage of this.
The nature of the question applies more to classical performance rather than improv (at least that is what I'm interested in).
So here is some background to illustrate where I'm coming from (what's on my mind). I have always found it easier to learn a song and commit it to memory before attempting to include all the expressive markings indicated in the sheet music, such as dynamics, accents, etc. It seems reasonable to me and has "worked" in the sense that eventually I get to a performance level, i.e. the piece is memorized, clean, can be played expressively, and I can even improvise by playing with the basic components of the piece. This approach can be described loosely as 'Figure out what to play then how to play it', or 'Get the melody correct, then the directions'. I even have memory of past instructors guiding me in that direction but some of that could be me filling in memories. Back in high school I had a violin teacher who insisted on playing every note the very first time exactly as it is indicated, with accents, vibrato, dynamics, expressiveness. All these dimensions at the very first effort to play. He promoted the idea that if you start perfectly there will be no real practice necessary (my embellishment). Really what I think he meant is that practice time would be minimized. I'm not talking about a hour on one given day, but the months that go into getting ready for a solo performance. At the time this seemed impossible to me and a little obsessive.
Later in life I began to read about how "muscle memory" works and how we train ourselves by repetition. Clearly no one wants to repeat a mistake or a bad habit, that is counterproductive. But is it not the case that by practicing to play a group of notes in tune without proper attention to accents and dynamics you've made a type of mistake? Is doing things this way (learn the what then the how) a set up to only have to retrain yourself?
I follow my old violin teacher's advice w/r to playing fast. In fact all my teachers promoted the idea that to play fast you need to first play perfectly. But I usually equate this to perfect placement of the fingers in the instrument and perfect timing of the various body parts involved. Again, I take the position that it isn't much effort to add dynamics and emotion after the piece is completely memorized and at tempo. But I'm not completely sure that's true.
Anyone who has mastered an instrument knows it takes effort to learn each new technique, to learn the correct amount of force or pressure required to create different tones and volumes, to learn vibrato and tremolo. So is it even reasonable to expect anyone to play all aspects of a piece from the first attempt at the first note? Or is this the secret to expert performance?
Based on the above my questions are:
What approach do people take for working a piece of music up to solo performance quality?
Does anyone use the approach I attribute to my violin teacher?
Does anyone know of a scientifically proven superior approach to practice based on neuroscience?