The one time I'd steer clear of the coach is the early early morning peak – say 7.30am-8.50am when trains usually are truly crowded, and chances are you'll come across it difficult to enter together with your baggage. Volunteers can be found in the two arrival terminals and international departures. https://angeloecitf.bloggip.com/30559000/how-sydney-international-airport-taxi-limousine-can-save-you-time-stress-and-money