For diaper punishment I would use thick plastic backed disposable diapers.
Or at least some disposable diapers that crinkle a lot.
A disposable diaper even with some prints such as Abu diapers, Rearz diapers etc can look really cute on someone who is being diaper disciplined.
Cloth diapers are okay as well but you can make someone or a kid look so much more like a baby or toddler wearing printed ABDL diapers.
Or if they will fit in them put them in an actual toddler diaper such as Pampers Cruisers size 7, Pampers Baby Dry size 6 etc.
Even Gentle Steps diaper when you remove the cloth backing from them make a very good diaper that looks really babyish even though they are mostly all white.
The Gentle Steps size 7 diapers swell up really nice and get really squishy.
Some rules fo diaper discipline include.
1: Your diapers must be used as intended for poop and for pee.
2 You must not ask for a diaper change and instead wait for mommy or daddy to check you and change you.
3:No usage of the toilet and the toilet will be locked and diapers will be used instead.
4: If caught trying to use a toilet or remove your diaper you will get a spanking and the diaper punishment will be extended.
5: You will be checked and changed as needed.
6: At home you will wear no pants over your diaper so the diaper will be clearly visible.
7: You will get a diaper change even in public when needed.
8: your clothes will be chosen for you.
9: You will eat from a highchair and also drink from a baby bottle.