When we started the Flatcar PART ONE, I left with a picture of this car:
BEFORE
AFTER:
Here's a few others for the thread:
So come along and see what I did to get this car to the finished product. Flatcars, and Gondolas are notorious for jumping the tracks when they're empty. Here's one of my solutions:

I went to a machine shop that was tossing these oversize needle bearings, and they wound up under the flatcar. You can use the double stick tape weights and paint them as well. Next let's do the deck, we need the raw material:

Then we need to make it look like ti's been out there awhile. I prefer paint pens, they leave no mess and there's no overspray. I highlight it first, then add another color.
Then after the wood is dry, we measure to fit. Look hard, the color of the deck wood is almost the same as the desk:
Then we cut the wood after measuring:

Make a bunch!! You'll use them!
Then we glue them down, I used a thick CA:
Then I trimmed the edges for any excess overhang. If you want it really looking beat up, leave some of the wood hang over. Use a razor knife of some sort.
Then color the edges to match the deck.

Done:
Here's another one:
BEFORE
AFTER
Here is a picture of the Dull-Cote along with the chalk that I smeared on the deck before spraying. What a scary mess!
And another picture. Looks like a disaster right now, see what happens to it after we spray it and smear it with a brush:
So there you go, how I make 'em stay on the tracks, and get there after a few years out on the rails. Hope this helps someone a little nervous about changing the paint jobs on their cars.
One other little trick: Try the chalk on your rolling stock without spraying it, if you don't like it, use a damp cloth and wipe it off.