I've got a hundred year old half-plate camera with a leather bellows that's in pretty decent condition, but it also needs a little conditioning. I've read that Lexol works well and I've used it on other leather goods with success. They've also got a cleaner and their own version of neat's foot oil. I've read some iffy things about saddle soap and normal neat's foot oil, but Lemon Pledge seems to be pretty popular--everybody must love a lemony fresh bellows.