Can you scrub through physics/collision effects?

I am having a go at using collisions to throw a paper ball at someone's face and have it bounce off.  My first challenge is I cannot work out how to get the collision to work on my fairly complicated person puppet - it just goes right through. If I try "collide" tagging other simple puppets, it works fine. I worked around it by putting a collidable puppet behind my person puppet - it's good enough.

But I want the person to react on their facial expression, which means getting the timing right. At present as soon as I reset the scene the object starts dropping, so I cannot start playing the scene to work out if the timing is right. Is there a way to do this?

(I am going to try using a particle cannon next, so I trigger the paper ball within the scene. Hopefully that will sync the two up. But wanted to know if I am missing a better way to do this.)