visa free application prior to departure?

Hi, I have a ticket travelling Sydney-Bangkok (overnight stay)-Chengdu (2 nights stay)-Seoul on Australian passport.

Do I qualify for 72 hours visa free in Chengdu?

Is there anything I need to do prior to departure or just go straight to check-in? I read your info about getting transit permit but it is not clear on what I need to do and where.

thanks heaps!