Besides the direct bus service from Wanchai to Huanggang, Shenzhen, there is service from Jordan, Kowloon to Huanggang as well.
This is 24 hour bus service, taking about 40 minutes one journey. It runs every 10 to 15 minutes during peak hours, ever 15-20 minutes in non-peak hours, and every 30-60 minutes during the night time.
Kowloon Terminal is located at 8 Austin Road, Hong Kong Scout Centre (Exit C of Jordan MTR station).
You can find the maps and more information here.