Consider checking out the Email Purmutator to see what combinations of firstname.lastname you may haven't thought of yet.
Good article on OSINT for Usernames:
https://cylab.be/blog/121/osint-simple-tips-4-usernames
Username OSINT Apps:
- Spiderfoot
- Maltego
- sherlock
- profil3r
- linkedin2username
Also see:
OSINT Attack Surface Diagram for Usernames

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