You could certainly introduce the other post, attribute it to its author, and link to the source. After which, put it in block quotes to make it obvious that it's not part of your own text. (You will want to provide something more substantial than just the other text, however. For instance, a bit of commentary of your own.) It's also likely that not all of the other post would be appropriate for a new post.
What you shouldn't do is nothing more than a copy and paste without anything else. "Blatant plagiarism" may be "easier," but that doesn't mean you should engage in it.
In fact, even if it's your own text, you still need to provide the appropriate attribution and source link. Otherwise, you fall foul of what's called self-plagiarism.