Q:
If there is a direct bus from Guangzhou airport to Shenzhen, any idea location at the airport/ time schedule?

A:
Yes, there is.

There are direct buses from the airport to Shenzhen just inside the airport.

It sets off at:

09:50, 10:50, 11:50, 12:50, 13:50, 14:50, 15:50, 16:50, 17:50, 18:50, 19:50, 20:50

every day and it takes you about 2h to get to Shenzhen.

for the bus location pls ask the airport staff.