How do you get between terminal 2 and terminal 1 at Chengdu Shuangliu Airport?

Oh, actually, you don't need to take the free shuttle bus. The distance between T1 and T2 is just about 0.6 miles. You can walk to there directly. But if you have many luggage, you can take the free bus. The operating hours are from 07:30 to 22:00 at intervals of around 5 mins.
In addition, generally speaking, your transfer time is enough. Don't worry. :)