Sidehack, that mailbox looks GREAT!
As for my hoppers for the final details, I ground down some plastic molded Gondola loads, from Bachmann On30 gondolas. I'm really glad I kept those, because they're already moulded black, and in reasonable shapes. Once I ground them all down to fit each car, I coated them and white glue, and covered them with scale coal. As soon as they're dry, I can just drop them right in.
On the ends, they'll probably be slightly bowed, which won't look exactly perfect, but I'll be able to remove them much easier that way if needed.
The one car I decided to model empty, I dabbed some white glue at the bottom, where I thought loose Cole would still be after it was last dumped. Then, I sprinkled a bunch of scale coal over top of that, let it sit for a little bit, then upended the car to get the remainder out.
I think it looks pretty good, what an empty car should look like.
