Is the best/easiest way to get to major attractions the tourist bus going from Zhangjiajie centre?

You must refer to the eco tourist buses in the scenic area, right? Well, yes. They connect the major attractions in the scenic area to be a good choice for visitors with limited time. I remember their operating hours are from 08:00 to 17:30.

Although for 2 days' visit, you need to buy a combo ticket, because they don't sell tickets for separate spots. You can buy the ticket at the ticketing offices at the main entrances of the National Park, Tianzishan or Wulingyuan.