How to roll a coin across your knuckles

Put a quarter and balance the quarter on your thumb.

Place the quarter using only your thumb onto your index finger.

Hit the coin gently to make it roll onto your middle finger.

Hit the coin gently again with your ring finger to make it roll onto the ring finger.

Roll the coin from your ring finger and capture it in-between your ring finger and your pinkey.

The last part is to drop the quarter onto your thumb then bring the quarter toward your index finger and redo the process.