24 visa free transit fly to guangzhou train to hk australian

Hi with an Australian passport, can i fly to GZ and take the train to hong kong within 24 hours without applying for a travel or transit visa beforehand? Plane tickets from GZ to hong kong are really expensive, but if i pay for the visa and the train ticket from GZ to hong kong it's basically the same price as the air ticket.

Now I'm not sure if i should go bkk - GZ - hk, or just bkk - hk and skip GZ all together because of the visa.