While hitting your enemy use E to make your enemy attack dodge then click W for more damage, when the enemy use the flash you can chase it by using Q. But don't worry in chasing you have a slowing effects like Rylai's Scepter.

1.You can cast two times the E of Jax. First cast is longer duration, the longer it's duration the longer it dodge. Second cast to stun quickly but you can't dodge after that. 2.The E of Jax can only dodge the basic attacks not skill shots.