If you can use addon plugins and you have sufficiently recent moodle version (2.6 or higher, preferably 2.8), you can get what you are looking for with the Dataform module. Here is a quick description of the activity set up for this purpose:
- (Install the Dataform)
- Add a Dataform instance in the course.
- In the activity settings, set Separate participants to Yes.
- Go to the fields index.
- Add a file field with the name "Feedback" (or any other name that works for you).
- Go to the views index.
- Add an aligned view with the name "List" (or any other name that works for you).
- In the View template remove everything but ##entries##
- In the entry template remove the patterns EAC:edit and EAC:delete.
- Uncheck all the submission buttons.
- (All this will make the view read only for students).
- Add an aligned view with the name "Manage List".
- Set it's visibility to disabled (so that students won't have access to this view).
- In the entry template replace the pattern EAU:name with EAU:edit.
- Set the "List" view as default view.
Now you can enter the activity, go to the Manage List view and add entries on behalf of your students. The entry form will allow you to select a student (from the list of enrolled students in the course) and drag&drop a file. Once saved this entry will available only to the selected student (and instructors).
If you want to bulk add entries, you can replace in the view template of the Manage List view, the pattern ##addnewentry## with ##addnewentries##. The latter will display a dropdown of numbers and selecting a number will open in the new entry form the selected number of entries and you can fill in the student names and files and save all.
Or if you're feeling comfortable you can add a csv view and import entries for all students. Currently, you cannot also import files via the csv view (forthcoming), but after you added the entries you can go to the Manage List view and bulk edit entries and drag&drop the feedback files.