Question [Q] Advice Needed: Wipe TPT before selling it

I'm preparing to sell my TPT 1838-25U and would like to ensure that all user data is removed. Difficulty: I have made backups with CWM and want to make sure I know where they all are and delete them before selling so that another person could not restore to a previous point-in-time.

Can anyone assist and/or guide me?

Thanks.

Earl