Not a fan of them myself but the theory is the same across for any extreme band. You can drop tune a regular E string to about C at the lowest, it will have an impact on the tremelo system so you need to unscrew the backplate and adjust the screws that keep the spring mechanism attached to the body of the guitar. This can take quite a while to get right and retuning can be frustrating but not impossible. The problem with drop tuning to C is that the strings become very loose so you will need to raise the action to reduce fret buzz. Heavier tones on drop tunings tend to work best with heavier guage strings eg .010 for the low string. The probelm is definition in the tone, D is ok but C is very difficult when it comes to maintaining clarity without specialist pickups. Most bands that drop tune will come down a half step rather than a whole step especially if they want to play anything technical (Michael Romeo from Symphony X is an exception to the rule but his technique is at least to the level of Yngwie Malmsteen and he uses custom guitars).