I cringe when I see shooters “breaking in” a new rifle barrel by hurriedly jamming cheap jointed cleaning rods tipped with every sort of cleaning jag imaginable back and forth through the bore with the frenzy of an amateur plumber trying to snake a clogged bathtub drain. For the average shooter with a new gun I agree with getting the barrel prepped at home. Using a bore guide, first remove factory goo and crud with gun solvent and patches only. Then, when it appears clean and shiny remove microscopic machining imperfections with a brass brush one caliber size smaller wrapped with a patch covered with a little JB bore paste/compound and Croil. Work it gently, slowly. Push a clean patch through one way, then clean barrel again with bore solvent until final patch is clean and barrel is bright, followed by a single patch with a tiny bit of oil. Your new barrel is now ready.
Go to range and fire a fouling shot. Clean barrel again with a patch or two. Gently. Proceed to sight in your properly prepped barrel.