Tip #1 use a cheap mountain bike you don't care about.
Salt does nasty things to the fancier metals used in mid to high end bike parts. Even the salt floating in the air 8 stories up caused serious damage to magnesium parts on my bike when I stored it on the apartment balcony one winter.
So, get a cheap but mechanically sound bike, keep it safe (clean and replace pads as needed), keep the chain kinda-clean (just as you suggested), and don't fret about the fact that after a few seasons it will be dead. Donate what is still working from it to a local bicycle recycler (if you have one), and move on to the next one.
I'm not calling a winter bike disposable, I'm saying that the entirety of a winter bike is a consumable.