Back in "Chapter 12" I sent my ideas for modeling scrap metal and wood loads for gondolas. (Also see RMC 8/13 for a detailed how to). Now I'll give some thoughts on modeling them as they appear the other half of the time, MTY. I'm also including a pair of flat cars. The models cover the 50's through the 80's so every one should find something useful to their era.
I show a variety of gondolas. The cleaning is most often done by the receiver. I found from experiencing the prototype that the job is rarely thorough. There can be anything from a little to quite a lot of residue left. THE CARS ARE NEVER TOTALLY CLEAN! Fifties period modelers, note the wood floor on the NYC gondola. These take a real beating as witness the gouges in the decking.
Here's a 40' wood decked flat car. I used an Athearn kit as the basis but, milled the cast on deck smooth (almost off) using a belt sander. I replaced the plastic "wood" with bass wood and then stained it subtly.
The image of 85' TTX car is purposely dark to show the color and value differences on the deck surface; all done with paint and chalk.
Hope you find something useful and/or entertaining,