Hate to say it, but Ludwig's is probably a terrible choice for that fight. Too much stamina use (you need to be dodging around a lot), and it only has good multipliers on attacks you're never going to be able to use against the boss (fully-charged R2 and the follow-up). If you've got any other +10's, which is likely if you're that deep into Chalices, you might want to just trade off.
Aside from that, his first few phases are easy if you just remember one thing: when he starts loping toward you unlock the camera and run like fucking hell. His AI is obnoxious as shit, and he will literally just keep stomping toward you trying to belly-flop on you for quite a while, and is too fast to escape locked on. Other than that, you can hang out at range and try to bait him into doing the attack where he keels over and starts blood-fountaining, which is extremely punishable (at least with a longer, faster weapon, but you should at least be able to get one good hit on his lowered head with Ludwig's).
His last phase you really need to get in close, because his range and the number of follow-up attacks he can do at range is simply too much. That's why Ludwig's stamina usage really becomes a problem, because you need to be side-stepping constant attempts to belly-flop onto you while still maintaining your attack rate. At very close range his attacks don't change that much in the last phase, it's mostly if you're farther away that he suddenly becomes a huge problem.
I'm just jelly though.
