I can't add much to this thread except to repeat some of the things Doug (PA24) told me and showed me via pictures about his barrel prep work. Even though he did more than a few barrels for me and shared plenty, there were still aspects of his work he preferred to keep to himself. I have noticed that same reticence with some other very high quality barrel bluers who have done my barrels.
Doug's main point with me was that too many craftsmen underestimate the importance of the barrels prep. Every single aspect of it. Ken just referred to 400 grit as the bare minimum for a field grade. Doug did a number of field grade barrels for me and he treated those as he did my best barrels.....and the final polish was with grits well over 1000. He would send me pics of the barrels in progress and they literally have a mirror finish.
Doug abhorred the idea of using power tools of any sort on the barrels he was bluing. All hand done. And although he was a big, strong man, I know he got tuckered out working on a set. All that hand finishing was tiring. And his fingers got destroyed....lol he'd send me pictures of those too!
He did his bluing cycles all in one day....usually around 12 -14 cycles and he'd be going at that from early in the morning until late at night. He was a perfectionist and I think often could not leave something to sit until it was perfect in his mind.
Doug knew the importance of the little details and would ensure that every barrel that left his home had been appropriately polished after the bluing process so the blue was where it should be and not where it shouldn't be.
He also never stopped trying to get better. He knew I'd had some barrels done by another gentleman who is an occasional poster here and known for his extraordinarily high quality workmanship. Every barrel Doug did for me, when I got it back I had to get it out along with a barrel or two done by the other fellow and talk to Doug on the phone, answering his questions about different aspects of the work and how they compared. Even though I think I have a pretty good eye now for quality bluing, thanks in no small part to both these craftsmen, I could never tell one's work from the other's except by my knowledge of who'd done what barrel. It was not evident in the workmanship.
And without getting too off topic, while talking about Doug, I just wanted to mention his attentiveness to packing things properly and making sure the shipping companies do what they are supposed to do. Anyone who had Doug work on something will know what I mean. He cared about it more than most owners! I already miss him.