try experimentation and practice. Play around with your throat and your tongue and you will find your style. and yes please use your diaphragm. If lets say for slipknot's style, ud have to use your voice so its alittle bit harder as its more tiring and youve got to still sing in key to the song but with a coarse throat. practice will do the trick. keep practising until u get it can already. don't forget that its not mindless uncontrolled screaming. there is control. if ure not careful you can end up fcking up your throat.