You can post the blog post as a regular submission, you can post whatever it is you want people to try as a Show HN, you can't post a blog post as a Show HN. That's in the thing I linked:
Off topic: blog posts, sign-up pages, newsletters, lists, and other reading material. Those can't be tried out, so can't be Show HNs. Make a regular submission instead.
Off topic: blog posts, sign-up pages, newsletters, lists, and other reading material. Those can't be tried out, so can't be Show HNs. Make a regular submission instead.