Alexi is pretty ****in' amazing. Work on his sweeps slow of couse and work your way up. Do them at a speed where you can keep a consistant beat and play it 100 times at that speed. Then push yourself to go a bit faster...again 100 times through. Then repeat even faster. Sweep arppegios require a lot of time and commitment but they're fun once you know em like the back of your hand.