So here's what you do:
1. Pick a scale that you can play across all 6 strings, starting from the 6th string (low E). I guess you could also do this starting from the 1st.
2. Find out with a metronome how fast you can play that scale without making any mistakes .
3. Once you determine your bpm, cut that in half and start your metronome at that speed.
4. At this slow speed, now you can worry about the best way or best sounding way to play EACH note. Maybe you realize that muting the first three notes sounds cool because it kind of builds up to the higher notes. You can also focus on WHERE to put your palm when muting, where to actually pick the string (different spots sound different), how hard to pick each note, if you're muting is on point. In other words, playing this slow allows you to really work on the actual SOUND of what you're playing rather than trying to play it at a certain speed. Focus on your vibrato on the last note, maybe try some pinch harmonics, or maybe use some legato. Go slow enough so you can be at your BEST. Then once you've found that, SLOWLY speed it up later on.