As far as protection goes, I read an article once several years ago about browning ML barrels. I don't recall everything it touched upon but I do recall the author stated his process of protecting the rust-browned coating on the barrel was to wipe it down with the automotive-grade carnauba (or carnuba ... whatever ... LOL) wax that is used on the modern (and soft) base-coat / clear-coat factory paint jobs. I recall it was pointed out the wax itself is relatively clear, easily covered well, and was preferred by the author because it sealed the rust brown coating but also allowed it to look natural and would last a while.
I guess you can say this was a "coating for the coating" ...
My only issues with this idea is that it would be fine for a rifle used exclusively for the range, but if used for hunting I know the scent of the wax, however slight, would be all too easy for deer and other game to pick up. Of course, this no doubt also applies to petroleum-based, linseed-based, and cooking oils. Maybe even beeswax has a scent of it's own, I don't really know. I use Hoppes regular oil on the barrel surface but I wipe it down well before I hit the deer stand/blind (or tree).
I've also heard of folks in this area of the country going armory-bright then spraying a coat of clear urethane on the barrell afterwards. Some folks may not like this option on our type of firearms but again, the best person to please first is yourself.
Anyway, these are just a couple of other options I've run across folks using in the past.