[Fixed]-Django: Adding Permission to an Specific Model Instance

You are looking for an object permission implementation. A good comparison is here:
http://djangopackages.com/grids/g/perms/

Shameless plug:
Heres my fork of a very popular per-object permission app: http://github.com/azizmb/django-authority

If I am getting you correct, what you need to implement is called row level permissions in Django. Have a look at this if it helps. http://code.djangoproject.com/wiki/RowLevelPermissionsDeveloper

I would recommend using Django Guardian for object-level permissions.