Vector X will work if you:
1) Don't have normal player controls active while the hurt animation is playing
2) Don't have the deceleration turned up so high that the character's x velocity will go to zero instantly immediately after your action sets it to a number.
BUT, If you want an easier way to do it:
every tick>IF animation hurt is playing,
sub condition>AND player character is facing left, then simulate player pressing right
sub condition>AND player character is facing right, then simulate player pressing left
This will ensure x movement in the right direction for the duration of the animation.