If you use the search tool, you should find much discussion on this topic. The "concours" approach generally speaking is to not apply paint to parts that were not painted from the factory. There are various other methods, some depending on the part, that are used in an attempt to both provide a finish that looks original and also to limit rust. Also keep in mind specifically for springs, that move, paint can be scratched off at the point if interference, and rust, then look worse than some of the other methods. I personally have used the gun blue method on springs with good results.