I must be missing something. I've hunted with blued and wood guns for more than 40 years, on clear days and raining days, and never had one rust. In fact, I've never had one rust anywhere that wasn't due to a lack of care afterwards. My grandfather and father always preached, clean your gun first when you get home, before you do anything else. I've done that since I was a child. It's that way I was brought up.
I inherited my grandfather's and father's blued and wood guns that were hunted with hard and none of them came to me with rust. Several had exceptional bluing wear that only added to their character, but none had rust.
It wasn't too long ago that there were next to no stainless steel and plastic guns to buy. It's a wonder that millions of blue and wood guns survived.
Google Inuit Hunters or Inuit Rifles. These folks that live in harsher environments that you and I will ever imagine, hunting walrus and seals in wet, frozen, salt environments, are mostly toting wood and blued guns. Many of them are long-out-of-production guns. And I doubt many of them have been sent off to some boutique for cerakoting.