NOW WE KNOW WHO HE LEARNED IT FROM.
One of the best changes in volume 5, yuuri winking at victor after he asks him to go sightseeing together. God and I just love now he doesn’t need the help of alcohol in his system to seduce the one and only victor nikiforov, with just A WINK he has it all under control. Also, imagine, victor trying to make yuuri wink just one more time, wanting to see it, but yuuri’s just too embarrassed and swears not to do it again.
(source.)