Hide grades for partially graded quizzes

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I have a quiz that has some essay responses and some multiple choice-type responses.  Canvas has scored the ones it can, and I am working on grading the others.  I want to hide the grades for everyone until I'm done.  I have tried changing the grading policy to manual (unfortunately, did it after the fact) and "hiding" the grade column.  The only grades that SpeedGrader thinks are hidden are the ones for which I have submitted grades for *all* the questions.  If I grade *some* questions, it looks like perhaps the students can still see the updated grade, which I do not want.

Any ideas on how to hide all grades for a quiz, even if a partial grade had already been published for everyone? 

I'm using the New Gradebook but the old quizzes.