I dunno what Xin Hua is in this case. The place for the visa is 华润 in 湾仔. DeePauk, didn't you already post a thread about this?
You can fly to SZ on the 8am flight, get to the consulate in wanchai by 3pm or so, apply for your rush visa, and come back to pick it up at 2 pm or whenever the afternoon service opens the following day. Go back to SZ on the subway and you can catch a 7 or
8 pm flight.
If you really mess up or have bad luck though, you might get to HK too late to apply the first day, and have to stay an extra day.