I've used Atlas and Polar to jumpseat back to Oz and the Far East numerous times over the last 8 years.
The only way you'll find out what the schedule is, is if you know a crew member or fill out the OAL request form. Once you fill out the form, you'll get an email from the lady in NY who deals with OAL requests. She'll also give you any phone numbers for Ops in whatever city you're catching a flight.
The hardest part has always been working out where to meet the crew. Once you manage that, the rest is easy.