Board Thread:General Discussion/@comment-24815992-20140717195349/@comment-11051098-20140718201227

Both Isshin and Kisuke fought Aizen in Fake Karakura Town. Nothing else is known, so we can assume they're both still at captain level.

Kisuke has been exiled for 100 years, so he doesn't wear his old Shinigami uniform anymore. I suppose that's what SirCraw means with "use his Zanpakuto without having to go into his Shinigami form". When he exits his Gigai, he is in his spirit form, or "Shinigami form".