Travel between Guangzhou & Hong Kong

Hi Anna,
Nobody seems to answer anything here! I have travelled from GZ East Station to HK many times on the "Through Train". It takes about two hours. You clear customs at GZ East then it is non-stop through to HKs main station for "inter-city trains", Hung Hom Station. There are many trains per day... I think several every hour. You still have to pre-purchase your ticket with ID, in person and arrive at the station an hour or so early. GZ East is a monster of a place but signage is plentiful these days so it shouldn't be too much of a problem.
Chris.