Early Airport Arrival at Guangzhou Airport

I have a 7 AM international flight from GZ, so I need to be at the airport before 5 AM. Is there a bus operating overnight to the airport I can take from near subway Line #1 near Ximenkou Station? Or could I take a taxi to some airport shuttle pickup point to avoid the cost of a taxi all the way to the airport?
How hard is it to get a taxi at 3:30-4 AM on a weekday morning?