I am not a big fan pf any kind of abrasives in my barrels, unless I am using them to fix a specific identified problem. And I have done quite a few pistols and rifles.

Tom's mention of the Beartooth lapping kit and process is really great for cutting restrictions or rough spots. The downside is that it will lap from the cylinder throat forward. Barrel, forcing cone, and throats. I once did a rifle to clean up a rough barrel, and found after doing the work I could now chamber some really heavy weight bullets. Just dumb luck that I did not wreck my throat. With a revolver it is 5:1, 6:1 or more depending on the number of cylinder holes, but it is worth noting.

Unless you use a bob like WR posted, you are more likely to round and polish very indiscriminately if you use a mop or even a patched jag. You'll get the land surfaces, the land edges, the center of the grooves, but probably not the inside corner of the land groove junction. The old round peg in a square hole. The bob will form more closely to the entire profile, and cut/polish more evenly and completely. It's kinda common for this inside corner to be a little rough, and gather fouling and lead. It's more difficult to clean this up without overdoing other areas.

I have flitz, JB and the Beartooth style kit that was marketed by Wheeler Engineering, with the Beartooth slugs. I never clean with any of them. I consider any abrasives to be a tool to fix a specific problem. You'd have to apply an awful lot of elbow grease with mag polish to wreck things, but if you use it every time you shoot and clean, well.........

Craig