Why rust a perfectly good piece of steel ? If your going to be water trapping just degreased and primed and painted will work just fine. Yea yea a rusty trap takes dye better, a non rusty trap takes dye too it just doesn’t get as dark . Dye them when they are new and dye them every year or two after that and they will eventually get dark. I can’t think of any other tool that you would rust on porpoise, protect and preserve them and they will last for generations. Pass this on to the boy and he will always know how to take care of new traps .
You obviously don’t have guns or at least any old ones anyways rust bluing was a preferred method of bluing guns especially high class ones, though it’s fallen out of favor nowadays in favor of caustic bluing
It’s distinctive in appearance having a glossy satin finish and is my preferred type of blue job
But to answer the original post after you soak in vinegar place your traps loosely stacked in a container such as an old cooler and place a glass jelly jar or other container with a couple ounces or Muriatic acid in it, in a couple days your traps will have a nice coat of rust and be ready for dye and wax
It’s my preferred method to prepare traps for dye and wax, though for water traps I nowadays just paint and go