I can't say I know how other magics work, but that's how the magic I wield works: as long as you know the subject and have a proclivity to that school of magic, you're able to cast.

Well, provided you have a catalyst.

( he gestures to the staff between them. )

You can channel power into the Boreas, and it will reflect back onto you with stronger potency. Then, you can use it on your target. Since you yourself know how your body looks and feels when you're healing, it may be easier for you to relate the two.