I'm going to be frank here, I don't claim to know everything about the muscular system, or playing the guitar. I'm simply telling you all what I've learned from experience as well as collaboration with other musicians.
I do not feel like I need to give any specific examples tab-wise of this one, really if you just pick a string (a high one preferably) to practice on, you don't need an example to practice the skill on.
I have been playing guitar for about 4 years now, along with that, I play guitarron, violin, drums, a little bit of bass, and a little bit of piano as well.
when I started out drilling I used to hold the pick parallel with the string. (so the flat side of the pick lined up with the string) much like any beginner would hold a pick. This technique is generally fine provided you are not planning to do any tremolo picking.
When you are looking to tremolo pick, you do NOT want to do a standard downward motion with the pick for each stroke, you will be slow and quickly exhausted. rather, when you start, hold the pick sideways so that the pick is nearly perpendicular to the string (a little bit diagonal is ideal, but for a beginner you more likely want the pick to roll easily).
When you start picking, alternate back and forth with the pick, if it is sideways, it should roll fairly smoothly over the string, but with still enough force to get a decent vibration going (again, if you can get it diagonal, it will be much stronger and louder).
TO GET YOURSELF TO BREAK THE LIGHT BARRIER!!!!!
If you really want that super speed tremolo, you will have to practice a lot. I've had the skill for about 3 years and have near perfect control over tempo and volume, but that is all in how i practiced.
to get going fast, even if you are a beginner you can achieve this, you will be basically vibrating the pick across the string, it may hurt a bit, but that is to be expected. This vibrating motion can be used in practically any muscle in your body (no guys, it probably wont work down there) to achieve high speed work in any instrument, but for high precision you cannot practice this way forever. You can show off with this for now, but you are not truly there until you can manage every speed of picking from 30 bpm to however high you can vibrate that pick.
there are a number of muscles in your hand and wrist that are making that pick move, but because you most likely have little use for them in your daily life, you have not put much work upon them, this is why professionals make it look so easy, because it IS easy. If you want perfect control over this skill you must start off slow, go at low speeds (again, try to get that pick diagonal, it gets much more volume and allows that string to put more force on your pick, allowing you to practice better muscle control) and slowly work your way up, this *should* work every muscle required to make the full motion, the vibrating only works about 2, and skips the others. This is why you are unable to make good control over tempo, because you are simply skipping between those two muscles and making no use of the others.
You will only master this skill with lots of practice, just like anyone else who is good at what they do, you too must work for your goal. Every good guitarist was once like you.