It's easy enough to get to Notorious by Armageddoning a town, but I was always averse to doing that. So if I wanted to get from Saintly to Notorious in a hurry, I started out by donating at a Baa Temple. I then sold the bones that I'd been collecting (mostly from Bootleg Bay, but some from Longfang Witherhide's Lair, and there's at least one other place that I can't remember) and then touched the Baa Heads in the Superior Temple of Baa. That was usually enough, but if I needed more, I'd go to the Temple of the Snake and kill the peasants in there. They won't talk to you; all they do is get in your way.

Oh, by the way, I found a note - if your party is Notorious and visits a Castle, they do get imprisoned for a year and they come out with an Average rep.