I've personally never tried getting hypnotized into wearing diapers but some people have said that they've successfully hypnotized a friend, girlfriend or spouse into wearing diapers and it supposedly worked for them.
I wasn't there to witness it so can't say if it's true but it's worth a try to hypnotize someone you know into wearing diapers or have someone hypnotize you into wearing diapers.
But if you want to wear diapers then you don't need to be hypnotized into wearing the diapers you can just put the diaper on and wear and use it.