Couple years ago, I walk in a Pp shop in HK. Chance upon their group GM. Had a chat, he put me on list for white 5711. I thought he was just being polite. I walk pass his shop almost daily on way home from work as its enroute. 1 yr later he call me, hello your watch is here, bing bam boom done.
For rolex, i have a good name card game. I intro my friends who buy iwc, cartier, jlc to the AD. I myself buy non rolex stuff also. Go to their vip events. Got my ss gmts, subs etc this way. I make sure to wear those watches they sell me back to the AD. Do things like adjust number of links, check the date change mechanism is in order etc. Build trust. Then they start to sell me steel skyD, daytona, deepsea.
For AP, much harder to get anything interesting but not impossible.
Some AD dont keep waitlist. I got some steel watches that way, just literally walk in to see see and if got just buy.
But in SG, i have no idea lol. just sharing hk experience.