My fatal flaw in this video is that I don't own a salopette akin to DDC or Toy March-- I have no idea if those may need a petticoat, but I'm asuming that they do. I didn't include that in the video though because I didn't want to steer others in the wrong direction.
Please leave a comment about if you use a petticoat under your salopettes, which salopettes, and a photo if you can! Salopettes are getting pretty popular now and need some info out there.
edit-- thanks for all the comments, I'm glad we have a good resource page in the works!