Patch Out. Used with their Accelerator if a quicker job is needed.
^^^^ This ^^^^ I have used Patchout with the Accelerator with very good results, no brush needed, just patches.
And in the event I can see a little copper in the barrel after this cleaning, a wet patch with Montana Extreme Copper Killer soaking the bore for about 15 minutes quickly eliminates it.
And as stated, don't use the Copper Killer with closed windows, and DON'T try to get your nose close to the open bottle to see how strong it is, it will burn your nostril. Don't ask me how I know this, LMAO.