I guess it's not all practice since I actually painted something...
I've only done a little airbrushing over the years, so I understand the process, but am not that comfortable yet painting an actual model. In the end, though, I did paint the NH 36' flat car.
I started with some spare Branchline passenger car sides as well as just trying some painting techniques on a box. The car sides weren't being painted for anything in particular, nor did I try to match any particular color.
I later mixed up a "grimy black" color for the flat car, and also tried some very fine dustings on a spare reefer body. I generally prefer to paint with straight black, then weather, but I didn't have black Model Air yet, and I wanted to start with the "airbrush ready" paints. Plus I want to see how starting with a grimy black as the base will work for me.
Working with Acrylics
Understanding the Airbrush
So now that the flat car is painted, do I decal it first, then paint the deck, or do the deck first? We'll see!