The inside of the depot won't be detailed, but you will still be able to see it somewhat through the windows. This model will be about 2'8" back on my layout, so interior detail is a waste of time, as is interior detail on anything not closer than 6" to the viewer. So what I'm going to do is to give the interior a coat of primer gray.
Here we have the model's walls, with the clapboard (outside) turned down. All we need to do is to give it some neutral color, and I like gray. I've tried flat black and other colors, but gray seems to be the one color that really causes the viewer's eyes to "miss it."
I could fire up the airbrush for this, but for this operation hand painting is fine. The finish doesn't have to be perfect. Also, I don't want to paint the surfaces that will be glued together, as it weakens the bond. For the airbrush I'd have to tape all of those surfaces. With a brush I just don't paint them. Do take some time with your model and decide what needs to be painted and what doesn't. Use a Sharpee marker and make a small dot on all surfaces not to be painted. For this project I'm using Badger Model Flex Primer Gray, which is an acrylic. I'm also using a stiff nylon bristle brush.
Well, something is wrong with the primer. My guess is that it has sat on my shelf too long and has permanently separated. Ok, no worries. This is inside and won't be stared at, so let's just use a bottle of cheap craft paint in gray. Paper towels are just mandatory for painting, and I always keep a roll handy with several sheets torn off and ready for spills.
Actually, that "cheap" paint, which I'll now call "inexpensive" paint gave great coverage, even with a brush! I painted the underside of the roof panel, and three of the outside edges. I did not paint the top because we'll put some type of roofing material on it.
Here I'm painting one of the two ends. Notice that I did not paint the corner areas where I'll be gluing the front wall. This will allow the adhesive a good "bite" and it will hold better than a painted surface. I didn't paint the areas that will contact the roof assembly either.
There! All the inside parts are painted gray. That's enough for tonight. I'm hoping tomorrow I can get to work on the front side as that is where the detail has to go!
1. Throw away old paint jars. They won't improve with time.
2. Brush painting is still an acceptable way to paint. Take time to develop your skill by hand painting less important parts of models such as the inside of a building.
3. Gray makes a good non-noticeable color for the interior of a structure, much better than flat black or bright colors.