Fastest way to cool chocolate

Hello all,

My name is Andrew and I am in the process of opening my first chocolate shop in Houston. My business will be creating 3.5oz 6x3.5" chocolate bars with a Selmi One tempering machine, and I had a few questions:

1. What is the fastest way to cool one chocolate bar? By cool I mean solid and ready to eat.
2. What is the fastest and easiest system to use, requiring the least amount of skills and experience?
   In other words, other options besides liquid nitrogen.
3. I have looked into Irinox blast chillers and was wondering if anyone had any experience or comments on the efficiency and effectiveness of the system?
4. Also, I have read earlier posts about a Holding Cabinet, and was wondering if this is needed?

Thank you,

Andrew