The trick also is to relax your hand as much as possible the more rigid your hand becomes the slower you will play those runs plus you risk injuring your hand!! and start at a slow tempo with a metronome and gradually build up the speed over a number of weeks/months..... the technique you use to play it slow should be the same technique you use to play fast!! aslo break the runs up into small segments and then add them together as your fingers become used to playing the runs..