Yasuo's dash has a set range going to and away from you when he hits you, if you learn this range by either studying him or playing him you can easily knock him up into your other abilities, as he cannot use windwall during his dash. Poke with your autos HARD at level 1, and he'll have a hard time farming and fighting back as he has nothing at level 1. Be careful of his HUGE level two damage spike. If you have the reaction time, as he dashes into your minions or you, you can Q right on his face for poke.
le Breathe in Your ult cannot be wind walled. But your W can, you can use 1 stack of your W at a time safely. And once his wind wall is down, you have SO MUCH opportunity to kill him. I fear for my life against a good Vel as Yas. Once I use my windwall, I have almost no way to defend against you, and that true damage is terrifying.
Last thing. Don't use your ultimate until he has E'd on you already, or you have someone or someway to get enough hits off on him. His Dash can dodge the Lazer faster than you can move it, so it's best to use it when there're none of your minions near him, he has dashed on you already and just recently, and/or your jungler helps you with keeping him still.
Hope this helped.