There is no direct shuttle bus from Guangzhou Airport to Huizhou. You should take airport bus to Guangzhou Railway station (to find the Guangzhou City Bus station or Guangdong Provincial Bus Station) or TIanhe Bus Station and then change to buses to Huizhou. The journey is about 2 hours and buses are easy to catch, for there is one bus every 15-30 minutes in both bus stations.

There are direct buses to Shenzhen city proper. Buses depart every an hour from 10:00am and just arrive at Bagua Yilu of Shenzhen. Hope it helps.