"I will be travelling to Kun Ming next year for 6 months".
Six month? Are you walking? Understand you like to have a motorbike when arriving.

any link to the article?

The trick is indeed S tubing known as well as swan-necks. Often the sink drains don't have them so you can make your own by using a flexible drain pipe and getting a nice S bend in it. Make sure the end of the pipe at the bottom is properly sealed so no smells can pass.

For toilets it is a bit more complicated. The toilet pot has its own S bend build into the pot. This is then standing on a drain that has a U bend. That makes two in a row and this makes the system to malfunction; that is the flushing does not work properly. Therefore there should be an air gap between the two bends. This is usually achieved by not completely sealing the toilet pot to the ground so air can move between the two bends freely. In this lays as well the problem. The pot not always drains nicely into the pipe under it and faecal matter ends up between the toilet pot and the floor and this creates the stink.
Most people will solve this by rekitting the pot but then the flushing is not working properly. The trick is to get the toilet pot aligned as best as possible and make a little dike with silicon around the hole in the floor. Make sure that air can still enter by not completely gluing the pot to the floor (Leave an air gap at the back) and make sure your drain from the toilet pot is not completely glued all around to the hole.
These air gaps are really necessary for a proper flush and without a proper flush the changes of faecal matter ending up between the pot and the floor increases.

SO MAKE SURE YOU LEAVE AIR GAPS (also this might look counterproductive it really is necessary and works.).

Was indeed a good sample of how to use forums.
Humor as well.
Maybe there should be a special section for classics.

Probably better to change the whole cylinder (The part of the lock that accepts the key) and get a full set of keys with it.