One thing that Trump can do is walk over to a camera, lift his hair and show he’s not wearing an earpiece. Then say that some people have implied that he’s ‘getting help’ at these debates.
...and just leave it that.
“I will not make age an issue of this campaign. I am not going to exploit, for political purposes, my opponent’s (Walter Mondalr) youth and inexperience.”
President Ronald Reagan 1984 Presidential Debate