You're eventually going to want to stray away from the riffle or slip force and learn this one. This
is the most natural of all card forces. Just spread the cards and let them take one.
It
will take practice but the more you try it, the better you will be. Unfortunately it will never ever
work 100% because if you try it on a sceptical person they'll likely just want to grab a card from
the top or bottom of the pile.
Having said this, as you improve, you'll be able to tell
which spectators to try it on and after a while you'll be getting it every time.