I've managed to use both however I do feel a visual cue would not be amiss ( maybe a small violin in the corner of the screen with an "I" button image and a "Q" button during the enemy's attack onscreen so the player isn't too lost as to when they should use it (Or as Whoopsie Woggzy said, some form of QTE could also be nice)
I still haven't managed to survive my first battle unfortunately