Paul Scanlon's blog post provides an in-depth explanation of how to use Gatsby's useStaticQuery hook to query data for a site built with Gatsby and Contentful. The post distinguishes between Page Queries, which are specific to individual pages and not reusable, and useStaticQuery, which can be reused across a site. Scanlon demonstrates how to create custom hooks to organize site navigation by querying for "top-navigation" and "bottom-navigation" links, which can be applied globally using Gatsby's wrapRootElement. He further explains the use of Contentful's Page Content Model, introducing a template field to differentiate pages, enabling conditional page rendering based on specific templates such as "home" and "blog." Throughout, Scanlon provides links to demo sites and GitHub repositories for practical examples, emphasizing the reusability and flexibility of useStaticQuery for various site functionalities.