Dear Dr. Cheese,
May I suggest some tricks to using the metronome.
Sometimes, when learning a difficult piece, it is better to set the beat to something other than quarter notes. For River People, which is a Moderate funk at qtr note = 104 and mostly 16th notes, I personally would start with the metronome set at 60 and each beat equals an 8th note. So every beat, you play two notes. While you are playing, stay alert to what issues pop up that prevent you from playing this perfectly and honestly address those issues before speeding up.
Once that is down, crank the metronome up gradually, not progressing until you have the current speed mastered. When you get to 104, put the metronome back to 60 and play quarter notes to the beat. Again, crank the metronome up slowly only after you can play the current speed perfectly.
The steps I described above are not going to happen in an hour or a day or maybe even a month. Your muscle memory is what it is and cannot be forced. Speed is not important. Playing it perfectly is. I would allow at least a week or two of daily or 2x daily 15 minute practice sessions for this item.
I second Spin Doctors suggestion to get it down on the fretted bass first. Muscle memory is best down by isolating technical issues before you combine them.
The piano piece I am working on is a classical piece in 3/4 time with a target of 240 BPM qtr note click My instructor plays this unstressed at 300 (3 note measure clicks at 100 BPM).) I am at 120, need to get to 180 by Tuesday.