I'm still riding my summer bike, as there hasn't been any snow yet. Unfortunately, one day someone got the great idea that pouring salt on the dry road will make a really nice joke. Then it rained, so there was lots of salty splash. Only once, and my chain & cogs have rusted, rear derailleur refuses to index properly, and the rear brake has jammed
The rear brake is my greatest worry at the moment - it takes a lot of force to start braking, then the v-brake will not open again, I have to pry it open

My winter bike has the same problem, but it showed up towards the end of the season, not after the first salt. Is there anything I can do to: a) get the brake to work smoothly again, and b) protect it from this problem in the future?