Sorry there are no shortcuts in this town for access to the best looking chicks. You will have to spend the money and I mean serious money. Like someone said above, HK has a lot of rich guys as can be noted by the dozens of Ferraris and Lambourghinis cruising in HK.
The spending on tables at Volar, Dragon-I, Beijing, Hyde, etc, driving a really exclusive car, dining at the most expensive restaurants, and being at exclusive charity/fashion parties are not to impress the chicks but to impress the rich local guys.
Once you have impressed and gained the confidence of the guys of High Society, these guys will introduce you the world that most of us can only dream of, ie - private ktvs (no public names), private membership clubs (as you discovered), access to the famous models and actresses who work on the side, etc. Their world places high importance on high quality and high discretion as many of them do not want to end up in the latest tabloid issue.
Of course once you misuse their trust or cheat these guys, you will be quickly banished from this world that you might as well leave HK after tasting all those exquisite fruits.
Like you I stumbled into a private unmarked ktv in a hotel once. I could not enter as I could not produce a name of the person who was supposed to have introduced me to the place. The place was extremely discreet. No name markings on hotel directory, lift buttons, outside signboard, etc. I would not know whom to ask to get a reference to this ktv as I don't belong to the high rollers.