Gotta read your directions. I have Brownells parkerizing solution, got the powdered iron there also. But I am sure that any clean ferrous metal will do. Clean off the old axe, sharpen it with a file and get some filings. Might take a while to get a large amount though. FWIW my gallon of concentrated solution makes many gallons of working park bath. If I recall it was something like 20 or 30 gallons. After mixing and aging you just need to let it cool off. I always start with a cold bath, bring it to temp, keep the temp steady when the bubbles appear on the parts and wait until it all gets black. I would run some test parts first before diving in on doing the gun.
