You can take the subway from Expo Station to Prince Edward Station (note that you must exit at Tsing Yi Station and turn to Tsuen Wan Line). There is an exit at Prince Edward Station, which is the exit of Jindu Shopping Mall, and the overnight bus stop to Huanggang is next to Jindu Shopping Mall. Don't worry, Prince Edward is still very crowded at 1 or 2 am on Saturday night. This bus is very crowded in the middle of the night. Please ask someone if you can't find it. I suggest you take the bus home after midnight snack in Prince Edward. Because there are many things to eat nearby.

If you come to Hong Kong often, remember to apply for an Octopus at the subway station. Because all public transportation is available, you can use it at the convenience station and fast food restaurants. The most important thing is to go to the Expo (get off at the Expo station). If you go by subway and walk by subway, you can save $18 by using Octopus!