For Season Schedule, you have to get slot time approval before by send the telex to BJSCKCA and fill the Application Form for Schedule Flight and send to CAAC which you can find the address in the AIP China in Part Gen.
For Ad-Hoc Flight, do the same first step of request slot time and send the application to request permit at BJSZGCA.
I have never contact any agent to apply. Any question, please email me at
[email protected]
Bye.