So… yeah… uhm… Is that even possible to do in less than 2 days? 
I personally didn’t even bother trying to farm those. I finished the whole game, exploring everything (maybe missed some secrets, but I don’t really care about them) and my reputation is… At the first stage. Literally the first square that you unlock. After I finished ultimate, killed Ravager, Lokarr and Mogdrogen, I said to my self “LET’S MOTHERDUCKING (not a typo btw) FARM KYMON AND CRONLEY!”. Guess what? Ended up not touching them because I felt like it’s pointless.
I am not hating btw. Just curious how you farm them and if it’s worth to farm it (I’d only do it because of Nemesis though).
I once farmed Cronley’s Gang to Revered whilst farming Darius for rings, didn’t realise for sometime until I ran into Fabius :rolleyes:
Well, considering the troves for killing those faction’s nemesis aren’t as good as others, I’d say it would probably not be worth it for you then.
However, if you still want to try, I find the best way to raise rep with Cronley is just doing Cronley runs over and over, while checking the Devil’s Crossing bounty table first for anything that might be doable along the way.
Same thing for Kymon/Death’s Vigil, really. Just run Fort Haron over and over. Archon Barthollum tomb mixed in when you get bored of doing the same place, or just run both areas every time.
I find a nice bonus for grinding rep with them is that you’ll end up with a nice stash of dynamite by the time you’re done, especially if you check all the rubbish piles.