If like me you had access to a Qantas Lounge Pass, however were flying Jetstar you will need to access the Lounge in a Different Terminal.
Qantas Domestic Lounge is in Terminal 3 , the terminal that all its flights depart and arrive from
Jetstar along with Tiger and Virgin depart from Terminal 2.
You can go through Terminal 3 Security without a Qantas Boarding Pass and check yourself into the Lounge. The Lounge Staff asked to view my Jetstar Boarding pass didn’t scan my Lounge voucher which was strange.
It takes around 10 minutes to get to Terminal 2 from Terminal 3. You can leave through baggage exit ( wouldn’t try exiting through Security ) and walk to Terminal 2 via signs. I would leave Terminal 3 an hour before your Jetstar Flight