Re: blued it and now it's rusting
OZO... case harden color the wheel gun!
As for the Birchwood...I have had some success with it... Prep-work is the key.. and even then, most of the time... just when i'm about to give up with it.. i strip it all down again and do it one more time... holly cow... it works for the most part (kinda uneven)... one day im just going to call goofy and send my stuff to him for a hot salts bath! Its not worth my headache for cold bluing with Birchwood.
You can't prevent the inevitable.. only alter its time span!