Yes, it was harder than it probably should be but now that I've written a book in it I've got it down by heart. Probably needs to be more prominent in the docs:

    # doc1, the destination
    
    .. _introduction:

    Introduction
    ---------------

    asdf asdf…

Then in the source document:

    # doc2, the source

    In the :ref:`Intro <introduction>` or 
    simply :ref:`introduction`,
    blah blah blah.

I made snippets in my editor to help with common tasks such as this.