Hate to say it but... Suck it up and live with it.
It lives in a hot, salty, greasy environment.
It's gonna get stains no matter how careful you are.
Be aware that you can over scrub and compromise the integrity
of the porcelain. The stain is not just on the surface.
Keep it maintained from here on out and love it like an old battle scarred vintage rifle.
Thank you for your service.