Anything faster cutting that crocus cloth needs very careful consideration before you apply it, and even then it must be judiciously. The main advantage to highly polished chambers is longer brass life for those doing full length resizing. Because the case sticks less well to the smoother surface, it allows the stretch in the pressure ring to be distributed over a greater length of the case wall, with the result that it doesn't thin out as quickly. If you use a sharp reamer and through-bore pressurized cutting lubrication, you can get it very smooth and pretty scratch-free.
Flitz and other polishes have been shown to work partly by microscopically smearing the surface to fill irregularities rather than simply removing high spots (though they do do some of that, too). But it's likely removing and leveling the surface on the order of two to five millionths of an inch or so (2 millionths or less ripple is a typical mirror spec). It takes awhile to remove much material working on that scale. So Flitz is pretty safe to work with. It won't remove a big scratch, but can make its edges less sharp so it ceases to mark brass.
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