Can I use these post brackets to attach railing posts on top of decking?
Railing post should have been a prerequisite thought in the process of building any deck. As far as attaching to Aztec or trex product decking it is not sufficiently structural to withstand lateral forces needed for adequate attachment.  Which is why you can't find any attachment method, as it isn't recommended.
   Sounds like you made your own decision on your approach to the problem.  Unfortunately if someone gets hurt because the railing "let go" who would be at fault?
   My suggestion is to reinstall new posts either through the decking and attached directly to the underlying joist or surface mounted outside the decking perimeter with carriage bolts(zinc coated).  The Aztec decking "will" shrink with time and loosen any type of nails attached, so think about that.