On the weekend, I saw a Chevy Cavalier with a unique hood ornament: a kitchen faucet. Seriously. With a coffee cup underneath, glued to the hood. I'm not sure if he had it connected to his washer pump or not.
But seriously - "drip" testing is another method some people will use to trace flow patterns. Dish soap drops placed in a row, then go out & drive.
I think you'll get more accurate info from tufts though...