I've was taught that whenever you write a run of notes going up, you should use sharps instead of flats; And whenever you go downwards, you should generally write flats instead of sharps. My question is: Which accidentals I should use when changing keys while moving against the flow of reading?
For example: If I was in the key of C Major and I was writing a downward run of notes and temporarily went into they key of E Major (4 sharps). Should I express it in the form of flats (making it easier to read, but harder to see the key change), or should I write sharps (making it harder to read, but easier to see the key change)?
I originally went with writing flats because it seemed easier to sight read. But if I had chords in the left hand, I'd end up with a lot of sharps in the left hand and a lot of flats in the right.