I think if i had a pair of helpless, ticklish, feet tied up in front of me - I would spend a very long time not even touching them at first but just taunting my victim by explaining just how much torture they are about to endure.
“This is about to be the worst thing you have EVER been out through”
“you’ll think you can endure it but you can’t, but you will have to feel it anyway”
“you’re about to experience a new kind of desperation and panic, and there is nothing you can say or do that will make me stop inflicting the torture on you - in fact the more you scream, the more it makes me want to make it worse”
“you’re so helpless, you can’t move at all, I have your helpless bare soles staring right at me and i’m about to inflict your worst nightmare on you - and there is literally nothing you can do to stop it. mercilessly tickle torturing an extremely ticklish persons feet while they can’t move is an extremely horrible and inhumane thing to do to another human - I understand that but I will be doing it anyway”
“30 seconds of being tickled feels like an eternity - imagine what the next 3 hours will feel like”