Well, the Abandonment doesn't officially have that name, nor any official name at all. It's just a technique Bang uses to deal with enemies he otherwise can't, by focusing his breathing and pretty much dropping feelings of sentimentality as well as his survival instincts.
As for whether or not he used it, again, the only implication he did is him breathing in, which, itself, is only relevant because he originally used it on Gums and FU. But in the webcomic, Bomb went on a monologue about how strong Bang is when he gets serious, and they directly mentioned the Abandonment technique. Here, there was no mention, and Bang was very casual about the whole encounter. Personally I feel like a single panel that shows him breathing isn't enough to assume he used it.