Part II of this study covers the variations of loss mechanisms for not only cryocoolers, but also compressors. To do so, it is inevitable to understand the efficiency of a system in terms of percent Carnot and/or a coefficient of performance. Once readers review these concepts, the next step is how to minimize the losses and optimize the entire refrigeration cycle. As described in part I of this study, a GM cryocooler is employed to study the loss mechanisms in detail. By introducing the concepts of energy flow, work flow, enthalpy flow and entropy flow, it is fairly straight-forward to visualize the refrigeration process. This approach is effective to optimize the refrigeration cycle, and a numerical method is used to demonstrate optimization of the GM cooler. To review the historical background of GM coolers, the Solvay cycle is also described to compare efficiencies.