best way to clear android system while preserving settings?

[desura]

I sold an android handset and one of the selling points was that the new user could have some of my customizations.

But there's a lot of personal data on here.

What's the best way? I'm afraid a factory reset would wipe out pretty much everything...I tried creating a new user and none of the apps carried through.

 

[Ravynmagi]

Can you do the factory reset. Create a dummy Google account, to install the apps/customizations, then remove that Google account?