Which sequence to visit both areas is recommended? Are busses and bus stations easy to find?

As I know, one day is not enough for touring both Dujiangyan and Qingcheng mountain, so you are suggested to visit Dujiangyan and Qingcheng Mountain for two days.

If you reach Chengdu by high-speed train, you will arrive at Chengdu East Railway Station. Upon arrival, you can exit the station and walk about 440 meters to the subway station and take line 2 to Xipu station. From Xipu station, you can take a 30 mins high-speed train to Dujiangyan railway station. Then walk to Dujiangyan fast train station to take Dujiangyan bus no. 9 to the scenic area. After the visit of Dujiangyan scenic area, you can walk about 200 meters to Lidui Park station where the Dujiangyan bus no. 101 will take you to Qingcheng Mountain scenic area directly. The bus journey takes about 1.5 hours. After the visit of Qingcheng Mountain, you can take Dujiangyan bus no. 101 to Qingcheng Mountain railway station and then take a high-speed train to Xipu station. After arrival, take subway line 2 to Chengdu East Railway Station.