How to apply visa for indonesian who lives in Australia

Hi, i have a few questions.. Am traveling from Australia to hong kong on the 2nd of july n spend two nights there n heading to Shenzhen on the 4th till 6and the going to Zhuhai through Macau n then back to Hong Kong on the 7th till 10th of july. Could u tell me please how many entry do i need?
Is it possible to apply it on line since i'm indonesian? If not, do u think it's safe to send my documents such as pasport via post?