Sometimes you can only perform a routine in front of a live audience.
You cannot practice it without an audience.
For these types of effects - you must go over the routine in your head again and again until you understand everything about it to the point where you think you have performed it a hundred times. Only then will it become natural - and appear very smooth and polished.
I once performed a routine such as this to an audience of 120 people - at a dinner. I borrowed a $20 from one person - and convinced everyone that the bill had been burned - by his choice. After some byplay - I offered him a banana in place of the $20 - more byplay - then broke apart the banana only to find his bill. The audience was convinced it was the same bill - as the serial number matched.
I had read and rewrote this routine until I knew it inside and out.
I could visualize it so clearly - that I felt that I had performed it many times before. It went very smooth - everyone was entertained by it - and I had a reputation maker in my bag of tricks. I'm still working on this one - and will have this as my key routine for this type of venue.
Look for this at my next performance - you won't want to miss it.