This is just basic maintenance technique after each ride, unfortunately most rider in HK won't even have the facilities to perform this basic function.
I just want to add one more point, try not to wash your bike with water if possible, just wipe clean most of the dirt.
Personally I use WD40 (a mixture of light oil and water) to spray the chain and cog clean after every 4 to 5 ride and re-oil my chain with light oil.