The statement that tone is all in the finger is spot on. As far as sustain goes, I always find that the actual pick attack affects both the tone and the sustain itself. My whole style of playing has evolved around adding varying degrees of pinch harmonics to pretty much everything I play. You can go from 5% to a full on 100% but if you add say 20% to a sustained note and add a smooth wide vibratto you can hear the pinched harmonic overtone burn over the picked note and increase to sound almost like feedback - great for DI recording because you can't get feedback from DI. I find you can get almost infinite sustain by using a steady, wide vibratto without being overly fast. If you are playing on front of an amp a good trick is to face the amp when you want that extra sustain that spills over to feedback - lots of things affect it though like the room size and ambience, distance from the amp, pickups and angle to the speaker - when the feeback starts up then stop using vibratto and switch to the whammy bar. I used to do that live all the time - kind of specialised in feedback with whammy bar and harmonic dives during breakdowns and between songs - you can keep notes going for ages that develop into cool new sounds while the drummer or bass player do a solo or something. Hope that helps!