[quote name='Doddy' timestamp='1356226630' post='1908241']
I don't. I generally think about the chords when I'm walking.
[/quote]
This was my point. It involves a lot of thinking time if you have to decide what mode you use if chords change once or twice in every bar. On a tune like So What there are only really two chords in the whole thing. To keep things interesting then, yes, use the modes. There is plenty of time to think about what you are going to do. Otherwise, as Doddy says, work with chord tones.