Like many things in the Guntrade it is surrounded in mumbo jumbo to frighten people off .
Apply yourself and anything can be done , the late Tony Treadwell , a so called amateur sorted it all out and did good work all documented in his book.
Tony White (T R White Gunmakers ) does fine work.
He learned his process off Billy Lane of West Bromwich , who taught Ray St.Ledger. Billy got so well paid (NOT) that he packed it all in and went off to drive a Fork truck in warehouse.Easy to colour case harden using charcoal and leather /bone mixtures and lots of experimenting.