It can definitely shorten the barrel break in time but your barrel might not need it. Try the cotton ball test. Run a cotton ball through your bore (clean and dry beforehand), then look to see if any threads got left behind. A rough bore will snag threads. JB Bore Paste on a patched brush, about 50 long hard and fast strokes (change the JB'd patch about every 10 strokes) won't hurt any barrel but it just may not be needed.
JB turns BLACK with use and will react with brass/bronze brushes so just clean it out with a jag and patches or possibly a nylon brush.