PluralEyes
PluralEyes works a little differently with Vegas Pro than the other editing applications. To work with Vegas, you always start the project in Vegas; send the timeline data to PluralEyes; do the sync in PluralEyes; then send the sync data back to Vegas in a similarly fluid command. It's a round-trip process.
Here is the whole process, from import to export.
The PluralEyes interface will close and you will go back to Vegas Pro to find the synced sequence.