The local shop is actually doing some whole gun bluing with Oxpho Blue when it is too much trouble to fire up the tanks or wait out the rusting process.
It looks very good. I have not used anything done with it enough to see how it wears, but have hopes.
The Brownells bluing instruction manual, available in PDF from their site, goes into detail on how to do it. It is NOT just a swipe it on process as you would touch up a worn spot.