Curl has a point. Any moisture at all that gets under fouling will cause oxidation. Any corrosive substance, like chlorate or perchlorate deposits from corrosive primers MUST be cleaned out of the tube or tubes right down to bare steel, or it will dissolve the iron molecules in the steel leaving sharp edged pits - no matter what type of steel.

I used to use bwananelson's method (with a bore guide) of JB and oil along with lots of elbow grease & many passes. I stopped using this after learning too many passes with a rod damages the bore from flexing and rubbing down the bore. Until people started buying bore scopes, this "over scrubbing" of the bores causing damage was merely THOUGHT to happen. Now we know it happens.

I now use no brushes and only solvents that do the work without scrubbing. Scrubbing merely seems to wear away at the fouling and leave fouling itself from the bronze bristles making blue colour that seems to be fouling still in the bore, so we continue scrubbing, whereas if you let the chemicals we're use anyway do the work, there will be little to no rod damage as neutralizing the chemicals and re-oiling is all they are needed for.