I have not used any of the spray-on finishes tho I have read that some of them are really great. I noticed Brownell’s claims Gun-Kote is more durable than bluing.
The most beautiful bluing I have ever seen was on a very early Astra 400. It actually was blue, not black as most bluing jobs are. Very close was a model 98-09 Argentine Mauser made by DWM. I got it unfired from Walter Craig in Selma, Alabama. The workmanship was better than most custom guns. Considering those guns were made in the hundreds of thousands or even millions that is pretty impressive.
The work done by factories 100 years ago is incredible. We are pikers compared to them.