Rust is never your friend, especially with firearms… If you have a old blued rifle or pistol that is scratched, or maybe had some machining work done to a firearm and now have exposed metal, bluing will save you from rust. The easiest bluing I have found, is the Perma Blue Paste Gun Blue by Birchwood Casey. It has a great gel consistency which makes it easy to work with. And by using repeated coats, you can get a darker and richer blue if you want.
You can find the Perma Blue here.
