CuddleShy (An ABDL/Babyfur Twitch Streamer) took the time to make not only a prefab for VRChat using the Higher Poly Poofy Diaper model to share with everyone else who purchased these files, but has also made a good video going into detail on how to properly put it on your own characters.

I'll leave a link to both CuddleShy's Twitch and their tutorial video below this...

https://www.twitch.tv/kawaikashu_cuddleshy

https://drive.google.com/file/d/1ettfslPMflxU1ZBhEjKhbGNQAqIHl_i7/view