I recently did the SYD trip. Down on Atlas out of HNL (keep track of their delays); and back on Hawaiian with a lie down 1st class - several more were open.

You have to check in at the ticket counter very early, then intercept the Captain prior to Customs. Once you get that signature, the counter will charge you $75 departure fee and issue a boarding pass.

Hawaiian crew was specific to let them know I made it, or else he planned to come back looking for me. Nice to hear it, and then the seat was great.

Depending on day of the week you can come back via Brisbane. I couldn't find a usable option to come back on Atlas. But Atlas will take you, cater you a hot meal or two, and list you on the GENDEC. You might get a crew rest bunk room depending on the crew.