yes we have already had experiences together, we have more or less the same kinksA bit more Information would have been more helpful for the future reference. Such as what kind of a friend? Did it ever get sexual between you? Did he ever see you naked? Or even did you do something like this with or near him before?
Depending on your answers there could be many ideas..
Something simple as deciding to just sleep naked near him or in a diaper..
To something more complex like maybe getting on all fours and pretending to look for something while wearing a plug or similar