#models.py
class Foo(Model):
    ...

class FooModerating(Foo):
    '''
        Прокси-модель
    '''
    class Meta:
        proxy = True
        app_label = 'moderating'

#admin.py
class FooModeratingAdmin(admin.ModelAdmin):

    actions = ['make_moderated']

    def make_moderated(modeladmin, request, queryset):
        queryset.update(is_moderated = True)
    make_moderated.short_description = u'Отметить промодерированными'

    def queryset(self, request):
        return Foo.objects.exclude(is_moderated = True)

admin.site.register(Foo, FooAdmin)
admin.site.register(FooModerating, FooModeratingAdmin)