Already S-Off, need root on HTC One M8 Verizon
Found the answer. There's a support channel, #sunshine-support on irc.freenode.org. Just go in there and type !info ring, and one of the devs pretty much instantly responds. Or, you can just type !info getroot directly and let them get some shut-eye. Anyways, that will provide you with a link to an apk called SUInstaller. At the time of writing it's at: http://theroot.ninja/apks/SUInstaller.apk. But, if it moves, follow the instructions I just gave to get the current one.

Anyways, you install this app and it will reboot your phone (installing su in the process). Then, just download SuperSU from the Play Store and follow the prompts. Reboot when it tells you to and then give it about five minutes after the phone boots up for everything to finish loading. Then, you can use something like Root Checker (also available on the Play Store) to verify that you have root access.