I''ve been looking for a way to do that for a while now. The thing is, yokomen is not a direct downward cut like shomen. It's attacking arc covers a large area of the side uke of the attacking arm. If you irimi out into that side you need some kind of uke nagashi to deflect the arm or you will take the slap. I guess this is why most schools do the inside irimi. And the angle with which the strike is landing confuses me as to how a deflection should look like and with what movement?
is what can become the uke nagashi if you go through instead of stepping in on uke like shown in the vid.
We teach to practice slowly, make contact with the arm and then swing in / fold in the elbow joint and lower arm while stepping through.
Hard to describe instead to show. But in the end the steps, the feet are much more important than the deflecting movement of the arms. With some experience it is sometimes able to do this without contact.