no, it doesn't drain the doll at all. Your goal is to get the doll to disappear so he can't val tus you. you generally can't react to val tus to hit the doll, it's too quick now. if you mash a button, he can often beat it by doing another 6d or something. The doll draws back between those attacks and makes it hard for you to poke it.
I haven't played this matchup much recently, but 5b is probably the best poke for hitting the doll. that or 5a. But even dash 5a, the doll will pull back enough to avoid it and hit you in the face if he does another move. But no real reward, it's just a single hit. Whereas val tus goes into pressure which can go into a full combo.
the other thing is to try to get up and over the doll.