This was an experiment. I'm trying to reproduce the truly beat up look of an older gondola. Gondolas tend to get beat up from the inside, so the panels are dented outwards, hard to reproduce on a plastic model.
I hate to destroy an expensive model, so this one started out as one of those really cheesy non working High Speed display models. I find these from time to time in thrift stores for fifty cents or a dollar at most.
I cut squares of .005" sheet styrene to fit exactly between the rivet seams. Before I glued them to the model I tortured them by pressing them and poking them with various appropriately sized blunt objects. The overall effect is pretty good, I think. The down side is that it makes the task of getting the decal lettering to look straight a bit tricky.
N scalers on a budget should look into these High Speed models. Their underneath parts have to be cut, filed, and drilled out to accommodate your choice of working trucks and couplers. But they are perfect for practicing your custom painting skills. And you can put together a roster on the cheap.