With every passing year I get worse and worse about keeping the vehicles washed and waxed. :/
It has been my observation that much of the surface filthiness comes from simply parking them outside overnight (garage crammed with other ****); just about every night when things cool down the cars get covered with dew and that just grabs whatever dust is on the car- and blowing around in the breeze- and glues it onto the paint.
But as far as rust goes, I'd think Sconnie is just like here, and that means we have super salt-happy morons at the DOT and city road crews.
What I've seen on my pieces of junk is that rust happens from underneath and even from the inside out, meaning no amount of washing, waxing, and polishing would have helped prevent surface rust anyway. For example my F150 is the only vehicle I've ever had from new. I washed and waxed that sucker endlessly plus I know how and where to wash it (or so I thought) by looking at other F150s and seeing where they rotted out. So at the car wash I spent as much time blasting under the rockers and up and around the inner wheel wells than I did on the parts we can all see. There was always a little pile of junk gathered on top of the rear inner wheel wells and as a result of my always cleaning that out I didn't see rust above the rear wheel wells for many years; usually that's the first place I see rust on F150s. But the rockers on the x-cab got rusty first and they did so from the inside out; I've heard there is a condensation issue there.
All the washing and waxing in the world will do nothing for that. I'd have to have taken the interior panels out when it was new and treat the sheet metal from the inside with roofing tar, grease, undercoating, whatever. Of course the "rustproofing" from the stealership was nothing but a scam.