Another method which I’ve used, is to have the consultant mentoree write his/her notes in the vernacular project, but not do a S+R. Then the mentoree copies their notes, pastes them into a Word document, and the consultant mentor then uses Word’s Review feature to respond to the mentoree’s notes. He sends the Word document via email back to the mentoree, who makes any necessary edits to his notes.
A variant of this method would be for the mentoree to put the notes into a Google doc, which he then shares with his consultant mentor. The mentor then makes any comments etc on the mentorees notes, from which the mentoree then makes any changes to their notes in Paratext. Once a chapter is finished, the mentoree does a Send and Receive for that project.