It is a common idiom so yes I would expect the vast majority of speakers(native or not) to understand it, as they do for many other idioms, and those who don't once they see it to do so from then on.Tbh, "damning by faint praise" is cryptic as fuck. Lol. I doubt that even native speakers can understand it.
One might even say it would be a piece of cake, like shooting fish in a barrel.