Hi Mr. James,
It depends on which bus station you are arriving, since there are four likely destinations, the Fangcun Bus Station, the Jiaokou Bus Station, the Tianhe Bus Station and the Provincial Bus Statin, if you are not arrive yet, I suggest you to take bus to the Tianhe Bus Station or Fangcun Bus Station, since once you arrived, you can take airport shuttle bus from thses two stations to the airport.
Good Luck!