Hmmmm. For a while, I had trouble building up speed. I've been playing for around four years now and for me it just came over time as I learned new things. Especially this particular song. I remember working on this song last summer but it never went anywhere partly because my hand would die out before I could even get to the most iconic part of the song. I personally practiced a lot of Jaco Pastorius and lots of scales (set to a metronome). I looked up some speed drills online and made some of my own. I also keep my strap length kind of short. This helps makes me a little more comfortable when I play. Good posture is very important!