I'd never heard of barrel break-in before I came on TFL. I got my first '06 in 1950.
I have two rifles that are around 30 years old, now. About 4,000 rounds through the Weatherby '06; maybe 1,000 through the Sako .243. Both still shoot in the 1/2"-3/4" area if I do my part.
All I've ever done is spray a bit of WD 40 on a patch and run it through the bore, generally. Occasionally a copper brush and then a wet patch, a dry patch and then a damp patch. After about 25 years the groups were degrading a bit. I used the copper-remover stuff four years ago and groups returned to their original tightness.
You're from BATFE? Come right in! I use all your fine products!