Cleaning up ton of pages with the 404

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Scott Clark: Are these pages in site map?
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  Saurabh Rawat: nope
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  Scott Clark: If you have a list of these pages, create a temporary sitemap and submit it to GSC. This can expedite Googlebot seeing the 404 and deindexing the site.
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  Richard Hearne: A 404 is a 404. Adding conflicting signals via robots meta or headers won`t help. More likely to disrupt. Better might be to provide links to these 404s to nudge recrawl, either via html or XML sitemap.
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  Saurabh Rawat: then why all wordpress sites have noindex robots meta in their 404 page.
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  Richard Hearne: I cant tell you about WordPress, but I can tell you that Google reps have repeatedly stated that they will not index 404 URLs. They may retain for some time URLs which previously resolved but later 404`d, but that`s not quite the same thing.
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  Michael Martinez: Search engines may index dead URLs if they find links pointing to them. If you`re not serving "soft 404" via a CMS it may be better to redirect the dead URLs to an empty page that specifies "noindex" in the meta data.
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  Saurabh Rawat: Thanks everyone, I have also asked about this to John. It`s true - there is no benefit by adding noindex on 404 page.
  https://twitter.com/SEOGuruJaipur/status/1186936224289714176
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  Michael Martinez: What John said is that "noindex" will be processed at the same speed as a 404. That doesn`t mean there is no benefit to adding a "noindex" to a 404 page. Google may still list a non-existent URL in search results if it finds links pointing to it. Redirecting to a "noindex" page should eliminate those listings, which annoy some people.
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  Saurabh Rawat: okkkee.. SEO is not simple as I thought.
  One more question: Why SEO people want to remove 404 pages from indexing. Is there any benefit?
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  Michael Martinez: I don`t know of any actual benefit. I guess it would be an aesthetic issue for most people. So many people ask the same question in different ways, sometimes it`s hard to determine what they want or need.
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  Saurabh Rawat: Michael Martinez thanks