This is a pretty amazing video I just found. I believe this was for Young Guitar Magazine. Usually when the guitar masters show us their signature techniques they don’t really go into much detail. In this video Dimebag goes into perfect detail how he plays harmonics and how he does those crazy squealing dive bombs like at the end of Cemetery Gates.
Basically in his technique he flicks the string with his left hand, dives with the whammy, and then hits a natural harmonic on the way back up. It seems so simple, but seeing Dime do it close up is just magical.
Alexi Laiho uses this technique in his playing as well.