More than 50 years ago I was a very young sprog straight out of the RAF training machine having been awarded my wings after surviving the Piston Provost, the Vampire and the Varsity.
I was posted to the Argosy which was a brand new addition to the Transport Command fleet.
I went through the conversion course with a very experienced captain who had done several tours on the Lincoln and the Washington.
Our instructor on the OCU was a bit of an old woman and he was forever touching things and "following through" on the controls. My leader was due to be sent solo and I was sat on the jump seat ready to occupy the right seat for this momentous occasion.
So we were on finals with one engine shut down and the propeller feathered and our instructor's hands and feet were everywhere. To my amazement, at about 200 feet Steve extracted a long plastic navigation ruler and whacked our esteemed instructor across the back of both hands.
This got his attention and he let go. After landing, Steve told the man that if he was going to go solo then he wanted to do at least one landing on his own!
We duly dropped his lordship and went solo for a couple of hours. Nothing was ever said.
So, my suggestion is to carry a long plastic navigation ruler. During your pre flight briefing, explain to the irritating person in the right seat what is going to happen if he starts interfering with you aircraft!