Deified_Data posted...
Manus is giving me trouble (this is my first playthrough). Can you actually co-op Manus? I haven't seen any summon signs other than Sif's.
Yeah. Usual place for summon signs is the Oolacile Township bonfire, as StolzPhoenix mentioned. Tends to help if you have the shortcuts open, since you really, really want to have a full Estus flask by the time you get down there. And you're all but guaranteed to get invaded at least once.
Also, one thing I didn't know the first time was that I could have two summoned phantoms _and_ Sif in that fight. The fact they let you do this fight 4-on-1 kinda says something.