I started by cutting a couple of strips of .005 thickness styrene to fit in between the ribs. Then, I took the styrene strips outside and dropped them onto my concrete driveway (yes, the driveway) and rolled an old wallpaper seam roller over them a few times. Doing this embossed the styrene with little bumps from the irregularities of the concrete.
Back at the workbench, I cut the styrene strips to the required length, and glued the pieces right overtop of the original gondola panels. I then painted the gondola dark tuscan oxide, and decaled it as a Herzog (HZGX) car.
I got a bit more creative, and sprayed the gondola with chipping fluid. I then sprayed another coat of the dark tuscan, which I promptly chipped off with a damp brush, to give the appearance of the lettering being aged and worn away.
Speaking of scrap gondolas, the local scrap recycler on the layout has become quite the busy place for me to switch out. Things didn't quite turn out exactly as I would have liked at that industry, but it's pretty good. The main issue that I have with it is that the rail entrance that I would have liked to have there just didn't have enough real estate available, so a couple of compromises had to be made.
I really wanted the rail entrance to be at the front of the fence line so that:
a) the JSSX shortline would have handled the switching duties, and
b) the spur into the property would cut across the roadway at an angle, which I thought would have been interesting visually. In my mind, this was to be something like a rail entrance to a scrap yard that I'd taken a (bad) photo of somewhere in Detroit a few years ago
But there just wasn't enough room for the entrance to do that.
So, the rail entrance is at the back and the GT switches the cars in and out. Oh well, it's still fun anyway.
My scrap recycler industry takes only about 10 minutes for me to switch out - an hour on the fast clock - depending on which spots the incoming cars are going to, and the order they're in on the train. I've collected quite a number of different types of gondolas that can be spotted in there. And, as I've shown some time ago, I've made removable loads for most of them so the cars can go in empty and easily be loaded to be switched out.