Probably easier to achieve mental conditioning that doesn't need physical results to re-enforce it yes, there are files like this - Hypnocat on Etsy does good work.
"Sweetie, you wet in your diaper a lot of the time, especially when you're asleep.
Babies wet in their diapers a lot. That's why you wear them.
But don't worry, because we will change you when you need it"
She walks down the stairs and watches as he crawls behind her
"Mommy. I wike dis new diapee.
I don't 'member going pee pee in my diapee. I wanna see Daddy and Bice and Sam"
He gets down on the floor and starts crawling behind Mommy