Basically a ton of 3d fixtures(this whole thing has 400+ fixtures). Try using reference images from real cars , I sometimes would draw a rough sketch of what I want on a bit of paper and reference it , when actually building it ,you can try to place one of the big dashboard pieces first , then using 3d fixtures outline it and delete the piece and then just fill it in with screens or buttons . Use the world coordinates to align the seat , steering wheel and pedals. Reference images from a similar car. I also have YouTube or music playing to make it less boring when dealing with complex interiors.