Using a lead lap that is cast by pouring molten lead into the barrel onto a wooden rod will do a great job on cleaning up the rifling from the lands to the grooves. Using either 4/0 steel wool or Scotch-Brite will only touch the top edges of the lands and not get fully into the bottom corners of the grooves. This is OK because most if not all of the burrs or sharp edges are on the top and edges of the lands which is what you want to smooth up.
I have used the lead lap method with great success when the barrel was in rough condition and use 4/0 steel wool when I want to knock off any burrs and polish up the lands. You can follow this up with a very fine polishing paste on a patch if you feel it is necessary but for me the 4/0 steel wool is good enough.
