Hi @Rachel_S
Bottom line is that you cannot do this in Canvas.
Grade posting policies can be set at the course level or the assignment level, but not at the student level, You will need to, as you've already done, manually calculate those grades and manually share them with the appropriate students.
If you would like to see Canvas set grade posting policies down to the student level, you should create a new Idea Conversation in this Canvas Community.
Not the answer you were hoping for, but I still hope this was helpful.
Kelley
