Stoping rust

Hi all... My ride has been hit hard with cancer and I'm about to pick it up from the body shop because I just had the rocker panels replaced. So far the floor boards and what not are okay but do have a layer of rust.

I want to know what's the best method to stop the rust? This car has not been maintained properly and has been used for 13 cold and hard quebec winters. I won't be using this thing for winter but I want to stop the rust since it will slowly eat away at the metal, even if the car is stored.

First I was thinking about scraping off the rust scales, painting the suspension parts (for a clean look) and getting the entire underbody coated with oil as well as inside the door jams and hidden areas.

Then I thought about cleaning off all the floor boards by removing as much rust scales and using a very good rust paint like POR or whatever, and getting the other stuff (that we don't see) oiled. But I'm wondering if the paint will just hold the humidity in the rust and just basically advance the corrosion where an oil coating will "drain" out the humidity and freeze the rusting.

arrrghhh! Living in the snow belt sucks for this...

I called a POR-15 rep... I will get some Marine clean to make sure the underbody is free from oils and whatever after I'm done scraping the metal to make sure there aren't any loose scabs or anything. Then I'll have to apply some metal ready and once all that dries, finally a coat of POR-15 black paint...

POR15 isn't that expensive but sure will be A LOT of work though!