Thus being said, I was in a metal band for two years, and I consider myself able to play your adequate hardrock/metal junk.
The "Chugging" Is all about rhythm, alot of times stylized by a combination of single beats, and triplets. (Chuh, Chuh, Chuh-Chuh-Chug) with palm mutes the entire time, unless you want to make something ring out. I'd suggest practicing in Dropped D, as it will have all the same patterns as Dropped C, and it's easier on the tone and the ears. You'll hear mistakes better. Use a hard pick! Easier to get that tone you want. For practicing, I'd play without distortion, so you can pick out your mistakes, and adjust. If you can play it without being sloppy without distortion, you can use the distortion to add to your playing, rather than just cover up your mistakes.
That's about all I can think of.
