FacetWP includes built-in support for the SearchWP plugin.
How to use it
When SearchWP is installed, create a new Search facet (or edit an existing one). Change the
Search Engine setting to the SearchWP engine you’d like to use.
What is a search engine?
When first installed, SearchWP uses its default search engine for your site’s global search page. However, it also supports creating Supplemental Search Engines (read the setup instructions).
Supplemental engines are useful for creating fine-tuned search result pages. For example, you could create a supplemental engine for a Resources page that only searches through resource post types, their attachments, and specific custom fields.
Displaying the Facet
Like always, shortcodes are used to display facets.