Slow-Fast alternation is an extremely useful practice technique. And it’s exactly like it sounds: play something slow, then play it at tempo and continue alternating the two ideas. When starting to work on a rough bit, it’s important to spend more time on the slow part. Something like a 4 or 5:1 ratio of slow:fast would work well. Gradually the ratio can be worked down to 1:1. Slow-Fast alternation is best used with small portions rather than entire works.
I like to use this analogy with my students: It’s like a video game. The programmers write the code and design the game making it work exactly as they mean too, then the player executes the program and plays the game. The slow part is the programming, making your fingers do exactly as you want them; the fast is the execution, running the program.
Metronome, friend or foe?
Maybe both. Forcing tempo up with a metronome, even using slow-fast techniques, can sometimes lead to increased tension – especially with beginners. Use the metronome wisely, but if you feel that it is pushing you too hard and tensions enters your hands put the metronome down.
From my personal experience utilizing slow-fast techniques with technical exercises has tremendously improved my speed and accuracy, and I have not used a metronome on a tech exercise for about six months now. Developing good movement patterns seems to be king, and that can be done without a click track in the background.