If you can handle it, go to the Steppe and do all 4 weather mini bosses; Long Gui, Ochu, Yomi and Immortal. Re-spawning them is easy enough, once you've done all four, just change the weather and exit to the Historia Crux and go back in and you should be able to do all four again
Academia 400AF is really the best and fastest way to farm CP, even quicker once you have the fragment skill to get more monsters. Depending on the amount of fragments you have, visit the mystic in Serendipity and she gives you a skill to earn more CP per battle than normal
even though it's no use to me whatsoever as I've maxed out all roles for both :/ I have over 100,000 CP going to waste currently.