Original cold rust blue for Imperial (WWI) Artillery Luger

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I have a 1917 German Artillery Luger that I intend to restore to as close to original configuration. As a gunsmith, I have the ability to do the restoration, but I don't know the specifications of the finish.
I need to know how high to polish the metal prior to finishing, the recepie for the bluing solution, and the proceedure for its application.
Thank you for your help

Harry G. Walters III
Gunsmith - Lebanon, PA, USA