Using a bronze brush will give you a false copper reading every time.
Can you get your hands on some Sweets and a proper calibre jag where you are?
If not get yourself one of those loop type adaptors for your cleaning rod but make it a steel one, if it didn't come with one.
This is how I do it, with a brush, be it bronze ot stainless, make 1 slow pass to remove loose powder fouling, push brush out the muzzle and remove, dragging carbon back through the barrel is bad, then 1 pass with a wet patch of Hoppes No.9, push it out the muzzle and remove the patch, leave it sit for 5 minutes, then another pass with a wet patch and scrub back and forth half a dozen strokes, if blue, repeat. This may take a few passes. Once the patches stop coming out blue, you need to attack any carbon fouling, if there is any black on the patches, I run a wet patch up and down a few strokes followed by a dry patch until they come out clean. If the carbon fouling is bad, a soak overnight with Hoppes in the bore should work. If New Zealand is like here, Australia, the better foaming type solvents probably aren't available. Hoppes works really well on carbon fouling if left in the bore overnight.
When I say "strokes", that is one up and back pass, BTW.
If it doesn't improve with several passes, for really stubborn copper fouling, I use sweets on a nylon brush and scrub back and forth several strokes, up and back at least a dozen times until it foams up, let it sit for 10 minutes to work, it works much better if you can get it to foam. Follow with a dry patch, then run another wet patch and follow the same routine if it comes out blue. Repeat until patches come out clean. It should remove any copper fouling pretty quick, but you must follow it up with metho, because it is water based, metho will remove the water content, and then lightly oil the bore as you normally would.
Good luck and good shooting.