Bus from HK/Kowloon to Shenzhen Airport

1. Well, according to your departure time, you are suggested to hire a private car to get to the airport directly. It's the fastest and most convenient.
2. Or you can arrive at Shenzhen one day in advance. In Kowloon, you can take Tung Chung Line to Nam Cheong Station. Then take West Rail Line to Hung Hom Station and East Rail Line to Lo Wu Station, Exit A2. After that, pass the custom and find a hotel nearby. In the next early morning, take subway Luobao Line to the Airport East or Hourui Station. Then take shuttle bus to arrive at terminal buildings. This is an economical way.
You can choose the one you like.