In your thread you can do the following ways.
Hit Quote on the users topic.
You can do this for each and every user. After you hit quote you will come to a "post screen" click in the box under the typeing that is already listed and write your vote number "if applicable" and that you returned the vote.
You can create one large post. You can do it as follows.
@"username" i was vote number 21 thank you!
Here is a real life example.
@Trex I was vote number 21
@Johanna Already done
@ Admin thanks for the vote I returned number 342
If you have any questions ask me or a moderator.