First, you should grab the coin with 3 of your figure. nut only use the index finger and thumb to hold it. Put your left hand into your right hand, and use the first two finger to move this coin our and put it at the back side of your hand. If you are afraid of the coin will fall, you can put some sticky glue at the place you want to place the coin. The place has glue need to be close to your thumb for making the trick smooth. when you show the audience that there is no coin in your hand, you should place everything to the place it used to be. put your left hand into your right hand again. And blow on it. at the same time. using your thumb to move the coin back into your hand. don’t forget to use your index finger and thumb to hold it. then slowly open your hand to add more magic feeling to it. Make sure to put your hand a little bit up to the audience in case they can’t see the coin. Also, it will help you to hide your action which when you put and grab the coin.