Err.. no pickup line needed leh... came naturally...
I just go over to their counter and start asking them to show me the various type of perfume... then they spray onto those scent strips and let me smell... after a while, I say for em not for ba type.. they show me.. then I ask whether can spray on their wrists and let me smell... they say ok... so hold their hands and smell lor... (You can pretend the smell is too faint and bring their hands nearer your nose and mouth.. nearly kissing her hand liao..
)
Then hor.... you must be playful and make some gestures they smell damn nice or something... after that.. they will be laughing and their defences will be done.. so I tell them I need to check with friend in singapore first before buying.. purpose is to tell them where you are from... but before I leave... I just pop the question whether I can have their phone no.. I just say "Day la so dien thoai cua tao" (Here is my phone no.) and give them my phone no. They usually give me theirs...
So you see.. I just know one simple viet line only...
But seriously, I think that the Viet gals are playful and if you can create a fun and playful atmosphere, half the battle is won...
All the best!
Lugi