Thanks for the advice. However, I have now found a qualified fellow who does rust blueing.
I did it myself only once...back in the mid-80s....on a beater Trapdoor Springfield that had been chopped to carbine length...and I did use Birchwood Casey "Plum Brown", as the rusting agent. I used no boiling tank or steam closet...I used my bath tub and its shower head...and at times a kitchen oven....and it turned out very well....I was impressed. But no interest in repeating that particular learning curve.