What would be the best way to get from Nanjing to Longquan. Is there a direct bus?

I'm afraid no direct bus can take you there. By bus, I suggest you go to Nanjing Zhonyangmen Bus Station to take a bus to Hangzhou first. You will arrive at Hangzhou North Bus Station, where you can catch bus no. 516 to its terminal at local South Bus Station. Then at the bus station, you can catch the direct bus to Longquan.

Or you can also take a high-speed train between Nanjing and Hangzhou, but the trains are not as many as the buses. Upon your arrival at Hangzhou Railway Station, take a taxi to the South Bus Station to take the bus to Longquan.

From Jiuhua Shan to Longquan or Lishui, you can also go to Hangzhou first, where you should go to the local South Bus Station to catch the direct bus to your destination.