For mid-80's era operations, I have built some Intermountain ACF centerflow 2-bay kits (and have some waiting).  I also purchased an assembled model, but the weight that they use in those cars is steel, and does not work with the uncoupling magnets.  Since I can't figure out how to take the assembled kits apart without damaging them, I can't use them on my layout.  I was told that Intermountain is no longer producing the kits, but only the assembled cars, which disappoints me.  With the kits that I've already assembled, I've found that even with the weight I've added, they are still too light.  But it should be much easier to add weight compared to removing it, and I will try a few things down the line.  Other than the weight, these cars are pretty good to begin with, so little is done to upgrade these cars (other than trucks and couplers).

For mid-60's era operations, I have two-bay PS-2 hopppers made by Atlas.  Gold Medal Models makes a detail set for this car which includes a walkway, stirrups, and brake wheel for two cars.  While the brake wheel in this set is thin, it is void of detail, so I used a Micro-Trains brake wheel instead (you can get replacement brake wheels in sets of 12).

 

First, I disassembled the car, and stripped the paint off using 91% isopropyl alcohol.  I then removed the stirrups, grab irons, and horizontal bracing.  I also removed the brake wheel and  roofwalk, and plugged the holes in the roof with the mounting pins I cut off of the roofwalk.    

The results are pretty much as I expected.  The Atlas cars aren't bad out of the box (things like stirrups and roofwalks aren't grossly oversized), but the "spindly feel" of the detail items do give it more of a 3-dimensional appearance (if that makes any sense).  These details even pass the three-foot rule, meaning I can tell a difference in the details from three feet away.

 

Now I need to put together the grain elevator so that I have a place to deliver these cars...

To detail this car, I bent grab irons out of .008" wire and horizontal bracing out of .010" wire, and attached them.  I considered making the grab irons out of .006" wire, but I felt that it would look too out of place with the thicker-than-scale vertical styrene supports on the model.  I then attached the new roofwalk, brake wheel, and stirrups.  Finally, I added a piece of .010" styrene on the side where the uncoupling lever is mounted, bent a pair of uncoupling levers out of .008" wire and mounted them, and added a .010" wire brace to the stirrup on the opposite side of the uncoupling lever.

 

After the glued setup and I made sure that everything was in place, I added non-magnetic weight to the car, washed the model with dish soap, and painted the car in light gray.

For lettering, I purchased a set of Micro-Scale decals (60-486) for B&O covered hoppers.  As it turns out, this one decal sheet has enough to letter four cars in a few different pre-Chessie styles, plus two Chessie cars.  I would still like to keep factory markings on one or two of these cars, and that can be done as long as I can match the particular shade of gray on those cars.  Once the decals sat for a good while, I gave it a light overspray with Testors Dullcote.  In the future, I do plan on weathering these and other cars, but this is about it for now.