Buffing The Finger
Rather than just "flicking the finger" at someone, Buffing The Finger involves the individual making an all too ostentatious and elaborate show of buffing up or polishing their middle finger finger nail; this in itself should be seen as part of the overall gesture. Given that the gesture itself is elaborate, it would do no harm to embellish the overall presentation of the digit with a quip such as "I made this for you... can you see your face in it?".
I saw she was buffing the finger at me so I polished up my retort...!
Buffing The Finger
Rather than just flipping the finger at someone, buffing the finger is am ostentatious and elaborate gesture of polishing up the middle finger finger as and intro to the offensive gesture itself. The add elan and flair, why not include a quip such as "Can you see your face in that?".
I saw her buffing the finger and quickly polished up my response.