Thanks for your reply !
For the conception, I drawn the shape with the structure, a really detailed drawing with each airfoil profil. I listed things which constituate the wings: machine gun, undercarriage, tanks, radiator, etc... defining their location, and how to make something that will looks realistic.
For the building, this is simply a use a styrene sheet from evergreen, according to the blueprints with some adjustments. I mesured the exact size for wing ribs, longeron. In fact, everything is in the conception. I don't really know how to be more precise.
I'm on a new project of cutaway. This time, It gonna be a P-61 from Hobby Boss 1/32 again more details. I gonna start the WIP soon. I'll try to explain a much as possible steps of conception and building.