so .. how can they beat itachi and kisame [ I know they can but someone will appear and say Ama solos lol ]
Together they can counter all their main moves.
-None of Kisame's Suiton are a factor against any of these guys bar the Water Dome (since they can tank each and every one) (Which will drown Itachi so its a no-no for this fight) and Great Shark Bullet, which can be overloaded by Multiple Bijuu Dama as I highly doubt it can take 4 of them, or they can simply evade it with their speed.
-Kisame gets beaten in CQC by V2 B or the 3rd Raikage. V2 B already put a hole in his chest (Though he managed to heal from it) the 3rd Raikage would simply overpower him with his physical might and durability. Kisame can't hurt him by slashing with Samehada as he tanked a Bijuu Dama, and it'd take quite a few slashes to absorb the entirety of his chakra. The Raikage can use his arm to block Samehada's hits and he can separate Kisame from the sword using his strength (Similar to how Gai did it when they first fought) and run him through with Nukite.
-If B fights long range in Bijuu Mode, Totsuka and Genjutsu aren't going to land on him, and he's already countered Amaterasu by switching out with a clone. If Itachi tries to close the distance and make it a close range match, B can use his whirlwind and blow him away, only to follow up with a Bijuu Dama.