Don't bother Brassoing them, just shoot them. Last year I got 1000 Federals that the cup was almost balck like those. Every one of them went off. I usually only load Win. 209's, but these were (practically) given to me, $12 for the 1000.
I'll tell you a funny primers story. Years ago we lived in Omaha and several years after we had already lived in the house we were in, I decided to tear out some shelving in the garage. I found a stack of primers. I was not a reloader. I gave the primers and a hammer to my son and said, "here, go out by the street and smack these". He did. So happens the guy across the street from us was an OPD and worked nights. My son had just smacked a handful of primers and this guy came running out, gun in hand, in his tighty-whities, ducking and dashing, looking for the shooter. It was too funny not to laugh (God rest his soul). Anyway, those primers were old - use yours.
I had ~1500 Federal 209 primers that were purchased about 1982 and stored in a less than desirable manner - a non-climate controlled basement workshop - until I picked them up in 2017. There were some light rust spots and corrosion here and there. Nothing that would interfere with installing them in a hull or keep them from chambering properly. Every single one of them (minus the ~250 unused ones that remain in my reloading area) worked without issue.
My wife and I shot some estates this weekend that had obvously been in water.
We had multiple shells that you couldn't tell where the primer was because of the discolor.
They all went off. Just something else to think about.
Rick in MT
I had two bricks of 1000 Winchester 209's that were in my buddies basement when it flooded, they were submerged in water for at least 48 hours. He passed them on to me several years later when he quit reloading, there was significant corrosion on the surfaces of most of them, I polished them up with a piece of scotch-brite and test fired 5 of the worst looking ones I could find. All 5 went bang.