In my humble opinion, It is more important to get the brass blean before running it through the sizer die, than after.
So the brass may not look as nice with micro-scrathes on it, but the only option I know of that will remove them is re-polishing.
It's up to you.
FOOTNOTE: I use a small jewellers screwdriver to remove the walnut media (and it drives me nuts)! I HAVE THOUGHT OF USING GLASS BEAD MEDIA FOR POLISHING BUT I DON'T KNOW IF IT WOULD CASE HARDEN THE SURFACE OF THE BRASS. ANY METALURGY EXPERTS OUT THERE?