Hey Rhys,
The Winton Sprint series is run by Winton themselves, rather than by a club who has hired the circuit. It's basically a case of fill in your entry form, nominate which class you want/are eligible to run in, and send it off with payment. Then you just turn up on the day in time for scrutineering, a 15min practice, and the drivers briefing.
Most sprint events will allocate groups, and you run in the same group every time. Winton just call it by session, so you just line up whenever you like. It's good that way as you can run with your mates if you want to. Once everyone has completed their first session, they call the second one and drivers can begin lining up again.
The first timed session at Winton has around 8 cars lining up single file at the start/finish line and are released one by one at 8 second intervals, running one standing lap followed by two flying laps. Every subsequent timed session has around 16 drivers starting 2 by 2, and it's then a drag race to the first corner. This time it's one standing followed by three flying. We had four timed sessions in total.
At the end of the day they take your fastest standing lap, and add it to your fastest flying (doesn't matter if they were in different sessions) to give you a total time. This is how the final standings are worked out for each class.