Unfortunately both methods are very difficult when you're trying to play an instrument with two hands.
Of course if you are not singing and playing an instrument at the same time, you have nowhere to stick your lighted ciggarette and may actually have to smoke it.
I am a singer who may sound better with one finger in my ear but like thousands of other 'singers with guitar' and singers in many other types of music have never felt the need to try it.
I am sorry I just don't buy it.