You do need a low level and mustering endorsement. If you have done fire water bombing or ag work or other low level flying, that will generally keep CASA happy. Various places can provide mustering training.
Generally the best or most popular mustering pilots have worked cattle for years on stations, jackerooing or whatever. However like all flying jobs it is a case of supply and demand. If there is a shortage of experienced pilots, then very low time pilots are often employed. As usual being in the area and readily available helps but get the paper qualifications first and be ready to fly dawn to dusk.
