In my experience there isn't a one method fits all. There are way to many variables to consider.....Design/method of rifling, quality of cutter, button or mandrel, quality of steel etc. etc.
There are several different techniques used for rifling a barrel - cut, button & hammer forged being the most common, and numerous rifling designs such as 5R, polygonal, 3 groove, 4 groove, 6 groove etc. A "break in" technique or method often suggested by a manufacturer for one type of rifling (Krieger cut for example) may be different for another manufacturer or type of rifling (Lilja button for example).
In my experience cut rifled barrels (even those hand lapped and produced from top quality barrel manufacturers like Krieger & Bartlein) require quite a bit more "break in" and shots before fouling is in check and top accuracy is achieved.
Button rifling and hammer forged rifling generally don't require the amount of break in or shots fired before fouling is in check and top accuracy is achieved. This too depends on a lot of variables including condition of the button or mandrel.
Using a good borescope goes a long way in determining bore condition and when break in or cleaning is needed..
