The only way to get that badge is to increase the number of helpful flags, which counts:
- The flags for moderation attention
- The flags for spam
- The flags for comments
Even after being a 3K user, it is still possible to get that badge. Being a 10K user probably help in getting the badge, as you can see the posts flagged from other users, and flag them if you agree, or invalidate the flag if you disagree.
As for flags for moderation attention:
- The "not an answer" flag should be used for comments and related questions written as answers. It should not be used for wrong answers, but it could be used for answers containing merely a link (even if the users who wrote the answer commented about the link being helpful for them); in the latter case, I would suggest to first writing a comment about expanding the answer and, only if the user didn't update the answer after X days, flag it as not an answer.
- The "very low quality" flag should almost never be used: If a question is that low quality, it is not a real question; if the answer is that low quality, it is not an answer.
That flag is intended to mean something about the user, not about the posts that user wrote: The quality of his posts is always so low that something needs to be done for that user. I will personally mark it helpful if the flag is being used on questions closed as off-topic, not constructive, and not a real question at least one month ago. Other moderators could handle it differently, though.
- In general, don't flag for moderation attention for something that you can do or for something that requires moderators to evaluate the correctness of the answer. The task of moderators is not evaluating the correctness of answers, for which a better tool is voting.
- Since there are queues for questions voted to close, and a queue for re-opening questions where edited questions are automatically added, use a flag for moderation attention only when the question is not getting closed and it is very bad, or a closed question has been edited but not re-opened quickly enough.