In my case, can I make use of this direct bus service from Shenzhen airport to HK Airport?

Hi,
I plan to travel from Guiyang to SZ by China Southern Airlines and then somehow reach Hong Kong and take an international flight from there operated by Jet Airways.

Thus, while transiting from Baoan Airport to HK Airport, I am not a passenger of either airlines. If yes, then, is there a way of booking this leg of my travel online, just to avoid last minute hassle.