If you have a choice, avoid using Sydney for domestic-international or international-domestic transfers. The two terminals are not next to each other and require an annoying shuttle bus/taxi ride between them. In some instances you might even have to carry your bag from the intl to the domestic terminal. Melbourne Airport is the best for this kind of transfer because the domestic and international terminals are connected. Brisbane is also better than Sydney because even through the terminals are not connected, the transfer shuttle is quicker and less crowded. Just my advice. It's too bad that Australia's main gateway is so hard to navigate.