Here is some barrel break in tips from Pac Nor, a quality barrel manufacturer:
"For best results, of course, it is necessary to 'season' it and use proper cleaning equipment. We like the Dewey coated rods, a good bore guide, copper/bronze brushes and cotton flannel patches, the appropriate size to keep that jag and rod in the middle of the bore. You will need a good bore solvent, like KG 3, Shooters Choice or CR-10 to loosen the fouling, followed by a scrubbing with Holland's Witches Brew or KG 2. After cleaning, nullify the solvents with rubbing alcohol and patch dry. Finish with Tetra Gun Oil, KG 4 or Holland's Bbl Break-in Fluid. Never shoot a dry bore as this will greatly promote copper fouling.
Chris recommends:
Shoot one, clean, for first ten rounds; shoot three, clean, for next thirty rounds; shoot five, clean, while working up load. Allow bbl to cool to the touch before testing a new load to avoid unnecessary throat erosion."