protection

I came across this site today, which has in depth explanations and guides for detailing. How to Detail a Car Step by Step - Detailed Image

I wonder ... since car makers do this less and less properly: is it worth getting some cans of fluidfilm & permafilm and giving the undercarriage plus a few of the accessible holes some good spraying to protect against rust? I drive it in winter, too. I'd love to do this myself, because little...