I recently assisted a client converting from using Federated Users that authenticate using ADFS to Standard User with DirSync and Password Sync. This Post is very helpful, http://social.technet.microsoft.com/wiki/contents/articles/17857.aad-sync-how-to-switch-from-single-sign-on-to-password-sync.aspx
What we found that converting the domain using the Convert-MSOLDomainToStandard –DomainName <federated domain name> -SkipUserConversion $false -PasswordFile c:userpasswords.txt Command from the link above did not convert all users. We ended up having to run the script at the bottom of the Link above to ensure all users got converted. After running the script we then forced another DirSync to get all passwords sync’d.