I wanted to ask if there is a away to end clean with the classic coin vanish so you can show both hands.
I just let them concentrate in my left hand while putting the coin in my back pocket but sometimes they see it.
By "classic coin vanish" I assume you are referring to a simple false transfer, leaving you with one dirty hand. In my opinion, in this situation, your best friend is misdirection in all its various forms
. There are countless ways to perform this type of classic routine. I prefer the "sucker" type vanishes when doing the false transfer based vanishes... these usually consist of at least one or two fake false transfers, and the coin is ditched/sleeved sometime before the last "transfer".
Here is a simple example of what I'm talking about that I will occasionally perform at gun point (usually for a younger and/or less skeptical audience). Take or borrow a coin and display it between your right index finger and thumb while showing your left hand empty. Say a few words to focus the attention on the hands and perform a fake
false transfer from the right hand to the left. Extending the left hand I ask a spectator (usually farthest to my right) to blow on my left fist and slowly open the hand. Of course, nothing has happened and the coin is there. (This is the perfect point to insert humor; e.g. "Wait, I think I know why it didn't work... did you brush your teeth this morning?" etc.) Under this verbal misdirection (all the while making as much eye contact as possible), I will do a simple false transfer toss (or half shuttle pass) from my left hand to my right, retaining the coin in left finger palm. Under the guise of stroking my goatee, moustache, or itching my forehead with my "dirty" left hand, I will either sleeve the coin (if possible), put the coin on the brim of my fedora hat, or drop it in my breast pocket while moving the hand upward -- this is done while the focus is now on the "coin" in the supposed right fist, which I usually extend toward (either the same or different) spectator (depending on patter) while ditching with the left... all that is left at that point is the reveal.
Like I said, there are literally hundreds of ways to accomplish this classic effect without any gaffs or what not. If you are new to coin magic and are interested in this, I would suggest picking up Bobo's Modern Coin Magic
if you haven't done so already.
P.S. Another way to end "clean" and show both hands empty is to use some kind of handwashing technique (which I like to do occasionally). Of course, the drawback with this is that you cannot show both hands simultaneously because one hand is always dirty... but a good handwash to a layman will be very convincing ^_^