Well I beat Sif but I hate the ghosts in New Londo. Four Kings should be simple because Beatrice wrecks them and I have chaos pyromancies.
Beatrice isn't very good against the four kings from what I've seen. Once you've got the water open you can sprint through pretty easy. Head up the stairs where the second pack of ghosts is, make a right and roll off the wall (I believe there's a big chunk of floor missing right around where you need to roll). You want to land on the bottom of the aqueduct. There's a ladder which you hopefully kicked down on a previous run through. Then you can sprint along the aqueduct to the tower where Beatrice spawns and roll off to head in. Only problem is there's some risky jumps that can fuck you over, and good or not, Beatrice isn't coming along. She'll get distracted by the ghosts and darkwraiths and end up dying/never joining the fight.
Also, it's a proven scientific fact that people who play fatty builds with lightning claymores are the actual Devil.
For a proper awesome build try this:
V40 A16 E35 S9 D16 I45 F30 R666
Full Black set, Velka's rapier, Parrying Dagger/Velka's Talisman offhand. Spells Vow of Silence, Karmic Justice, whatever (Heal maybe, or darkmoon blade but you'll need an alternate main weapon for it.) Rings whatever. Hornet if you're a dick (I'm a dick), Cloranthy, FoP isn't that useful since you're so light.
Join Darkmoon Blades.
You're Oswald now. When you kill someone spam Well? What is it! For a silly theme build it's actually pretty strong, I usually win 8/10 fights when I forest gank, including 2v1 (Even a 4-way freeforall once with the NPC bandit and a Darkwraith/Forest hunter. Killed them all)