Using Swift with manually reference counted Obj-C?

Hi all, searching on the interwebs I didn't find any guide that might explain how to use Swift with manually reference counted Obj-C.
Is there such a guide?
Or is the idea too outlandish?

It should work just the same, really. ARC is a per-file concept, not a per-project one. Some of the existing system frameworks you use every day with Swift are manually refcounted for various reasons.