Currently, there is no direct bus could be used. It is suggested that you take the shuttle bus Line 1 to Shenzhen Railway Station firstly (one hour). Here, please catch a bullet train to Guangzhou in 70 minutes. The train terminal is Guangzhou Railway Station or Guangzhou East Railway Station, both of where you could take the Guangzhou Airport shuttle bus to reach the airport in one hour. In this case, at least 4 hours is needed for transfer.

i sugget you to take a Airport shuttle bus to Guangzhou coach station , there from coach station you can take walk to railway station for 100 meter , there you can see china southern airlines office , there you can take airport express bus to airport,
or you can take a MRT to airport from Guangzhou railway station
have a nice journey

There is no direct bus or train going to guangzhou from baoan airport,but you can take the subway come to luohu then change the direct train going to guanzhou
hope it helps