I'm writing a PS script to update them to be searchable and to add aliases, and the task is taking a while. I need to find the managed properties that exist without manually searching for them or trying to figure out all the conversion logic (e.g., replacing all special characters, adding OWSTEXT text columns or OWSDATE for date columns, etc.).
I was wondering this could be automated with some C# or JavaScript code.
Try putting this in your REST search call: &refiners='ManagedProperties(filter%3d600%2f0%2f*)'
It will return all managed properties of the found item as refiners (you could restrict your query to content type for example). Have a look at this search tool. It is great for testing search queries and seeing all managed properties: http://sp2013searchtool.codeplex.com/ (the above method is also used when you click on "View all properties" on a search result). Here is some info about using this tool and finding all managed properties: https://blogs.technet.microsoft.com/searchguys/2013/12/10/how-to-find-all-managed-properties-of-a-document/
