Don't know about brake fluid. I know lots use carb cleaner to rid the bore from the factory gunk they put in it for shipping/storage. However you must follow the carb cleaner with a good soaking (several patches) of a decent quality gun oil or you'll have a rusty mess on your hands.

I'll just stick to my MC#7, Sweets or barnes Cr10 for copperand BC Sheath gun oil. I use some BF CLP as well, for certain applications.