I tend to believe that 'less is more' in terms of the treatment's aggressiveness, when trying clean up a blade of rust. For blood on a blade, I'd start the same as if it were a kitchen knife used for cutting raw meat: with a dish soap & water wash. Then, for the loosely attached red rust, scrub the blade with some baking soda (my preference - I've liked how that works). Baking soda is just mildly abrasive enough to knock off a lot of the soft red rust, but not hard enough to scratch the steel in doing so. The fine steel wool method would also work. Then WD-40 with perhaps some more scrubbing as desired (w/baking soda or steel wool). Then, when it's clean & dry, oil the blade.
I can understand using vinegar if you actually want a patina on a new & shiny blade - I've done that myself. But just know that while it's in contact, it'll also generate a little more corrosion (rust), in combination with leaving the black oxide on the blade. Own the consequences of that, if you choose the method. A new blade can survive that without much long-term consequence, so long as the blade's thoroughly cleaned up with baking soda to neutralize the vinegar, and lots of rinsing off under running water. For a blade that's already heavily rusted and likely pitted as well, I'd avoid that treatment, as the 'patina' is already there and doesn't need any more help. And it certainly doesn't need any more etching or pitting either. Pitted steel is more difficult to rid of all the accumulated stuff that generates more rust, as the pits provide more places for it to take hold more deeply, and therefore harder to clean up.
