I have a tip I’d like to share with reference to the articles on this topic in OGR Run 335. I painted the “wall”, behind the passengers in my MTH B&M Doodlebug, flat black.
This creates the illusion that the interior is darker, adds depth and makes the passengers more visible. I don’t paint the seats for good glue adhesion, making them more visible, too.
I used Beep People for the project. They are too wide, but were not difficult to cut in half (head to toe) with a utility knife. Just don’t tell anyone the same people are on both sides of my Doodlebug!
John