Sir Ian has it covered very well.
My primary rust issues are things like VARF when the armor is used all day, put in a box, used the next day, put in a box, I get home, unload the car/truck (sometimes), shower, go sleep, go to work, Monday is trash / recycles / kitty litter / etc so typically chores then bed (unpack/unload if I didn't already), Tuesday is work all day, and by Tuesday I get to start cleaning. The rust is minimal, mostly inside due to sweat (sweat is salty / salt water) and where the liner rubs off from contact with the mail / other plates. A couple days of 6-7 hours at 90+ degree temps makes armor rather icky. Even then, it's light rust, no pitting; the bright orange, "early" rust that is easy to clean.
Outside, very light surface rust I just wire wheel off, since my armor is basic unpolished mild steel - and I have a lot of plate surface area to clean. The scotch-brite that Sir Ian mentioned works just as well and is better for polished / carbon steel. When I wire wheel off any one piece of armor, I do the whole set. Somewhat OCD with that.
If there's no rust outside, it's just a basic wipe down with an oily rag to remove any sweat / moisture, and a fresh spray of oil. Since it stays on the stand (with air circulation), it isn't as prone to moisture issues as being in a box.
I'm sort of the "middle ground" between Sir Ian and Sir Edward with maintenance.