In the army (okay, I know, not an airplane thing), we used two fingers (in a "V", not one finger on each hand
) pointed at the eyes to indicate headlights on or off (when they were supposed to be the other). I have used it a couple of times with mixed success.
Walking away works if the pilot isn't following your signals, but doesn't help the pilot if he doesn't know his lights are on.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.