Speed comes from mastery. There are no shortcuts to speed.
I am a self-taught guitarist of probably-average skill. While I don’t have a dedicated routine of consistent practice these days, I often pick up the guitar and noodle on a tune during the workday. It’s a great way to relieve stress and to pause, take a break, and refresh. Mostly I just play whatever’s in my head, but occasionally I will get the urge to learn something new and complicated.
Last year, I decided I was going to learn The Call of Ktulu, an instrumental track that closes out Metallica’s 1984 album, Ride the Lightning. The fingerwork for the intro seemed complicated to me; usually my grasp of basics and fundamentals allows me to learn new songs without much trouble, but this particular fingering I wasn’t used to.
As a result, my initial efforts were painfully slow. I would miss notes, and my fingers generally felt sluggish and clumsy. I gave up early the first day, thinking maybe I would try learning another song instead.
But the next day I came back again. I was curious, and with the pain of the previous day’s struggles behind me, I was inspired to try again. It went marginally better. I had fewer missed notes, and my fingers felt more sure of themselves. Within just a couple more days of casual-but-regular practice, I was actually able to play the song at full speed, with confidence.
Speed comes from mastery
The only way to do something quickly is to first learn how to do it correctly.
Much of my frustration in the example above came from trying to push myself to play at full speed on the first day. My fingers were not yet used to the notes, and so the result was playing the incorrect notes (or missing notes).
If you try to force the quick before you master correct, you will end up with the wrong results. You will learn bad habits and poor technique, and it will be hard to undo the damage later on.
It doesn’t matter how fast you run, if you’re headed in the wrong direction all you will do is get to the wrong place really quickly.