Pure Copper Chore Boy wrapped around an old bore brush, dry, usually at the range while the gun is still hot. Gets barrels and chambers really clean. After that a normal cleaning finishes the procedure.
A close second are the Hoppe's Tornado brushes. I like these for cleaning heavy fouling from shotgun barrels after shooting a lot of buckshot and slugs. you can clean using a short stroking action and reverse them in the barrel without having to worry about them getting stuck in the barrel.
I have not seen any scratched bores using either of these techniques.
Just my .02,
LeonCarr