I spent a long time trying to figure out the 'perfect' way to hold my picking hand, strike the strings... etc.
It was a total waste of time.
For one thing; there is no 'perfect' way for everything that you need to do to play guitar. Some techniques require your hand in one position, others in a different position.
Like has been already said, keep your hand comfortably positioned and just do it over and over and over. The only thing you should concentrate on other than repetition is keeping your movements economical. Meaning; as small as possible to accomplish the desired effect.
Speed and accuracy will come from repetition.
Only other advice I can give is what others told me when I was working on speed... besides just 'keep doing it over and over'.
When playing fast, choke up on the pick. Only have a small amount of the picks tip sticking out from your fingers. The less pick you have 'under' the string, the less you'll have to raise your hand when changing strings.
Again' economy of motion. You mentioned watching shredders that looked like their hand was hardly moving. That's why. They are using the smallest movement possible.
Only practice can teach you that.
When striking the string, you don't need much of the pick to hit the string. When you raise your hand to skip strings, you barely have to miss the string with the tip of the pick, so you really don't have to raise your hand much.
I'll say it again, "Economy of motion", but you have to look at it in every aspect.
I'm not much of a shredder, I play mostly Classic Rock and Blues, but I wanted to have the technique to handle the faster stuff, and it took me a long time (years actually) to be able to 'shred' enough that I thought it was adequate.
Don't get discouraged, and stop over-analyzing it.... just play.