I was in the 'senior citizen pensioner' category when I first saw them "hand lapping" like that with steel wool; I'd been reloading and competitive rifle shooting since the early 1970's. Everything I had heard and read to that point said that only a fool would put steel wool in one of their barrels. Another childhood/'everybody knows' myth dies a sudden and unexpected death...
For those still fearful of steel wool, I get it. So try a safe experiment for yourself: grab a piece of 3/8" drill rod and mic an area of the rod. Then grab a handful of steel wool in a leather glove and go to town on the exterior of the rod with your bunch of steel wool. See how long it takes you to remove a thou from the diameter.
Ah yes, the ol' strands of copper/brass Choreboy cleaning pad trick. That and firing cream of wheat through the barrel... done that often, along with the Lewis Lead Remover with its screens.For those simply attempting to remove leading from their barrels, would brass wool be sufficiently abrasive to do the job and steel wool left for the job of lapping the toughest crud and tool marks from a barrel?
Powder coating bullets along with finally realizing that the most important fit when using cast bullets is a tight fit into the ball seat/leade has eliminated about 95% of my leading issues. Since working at MRC, when I do get leading now, if a bit of patience and the right cleaning solutions doesn't remove it, I'm not going to bother with the softer copper/brass scrubbing pad strands - I'm going straight to medium grade steel wool.
After what I saw at MRC and my experiment, I don't think I'm going to live long enough to do enough bore scrubbing with steel wool to make a minutiae of difference to the interior of a barrel. (but I'm also going to remember that steel wool isn't going to remove lead it doesn't touch i.e. leading/crud in the bottom corners of the rifling.)
As far as barrel corrosion and crude along with tool marks, I think I posted that after a lot of effort and scrubbing with coarse steel wool, I'd only managed to remove enough metal to increase the bore diameter .001" - and the tool marks were still very, very visible in that barrel.
Lapping can obviously have positive affects on barrels, whether to quickly remove tiny microscopic manufacturing burrs on edges (which shooting would eventually remove anyways) or to smooth out the edges of corrosion and pitting in the barrel. But attempting to remove crud and corrosion with steel wool? Thinking of the amount of time it would take to do that is painful to consider.
I have helped others improve really crappy antique barrels by pouring a lead lap and then starting with the coarsest abrasives and working their way up to the finer grits; those episodes took me pretty much a day of patient careful work at a vise at a bench. Maybe gunsmiths can rescue a barrel in bad shape much faster than a nervous guy like me who's worried about harming the barrel can.
But whatever effort it takes, a lead lap is going to do a much faster and more consistent job than a wad of steel wool wrapped around a worn out cleaning brush and dragged back and forth through the bore. Additionally, using a lead lap, pulling it back and forth through the bore tells you whether or not there are tight and loose spots in the bore and where they are so you can use your lead swage to eventually even everything out so that it is far more consistent.
I have zero experience with fire lapping, so I can't offer any personal experience regarding going that route.