Sounds like lots of fun if he can breathe.

Possible suggestions - things to try:

An enema for him before you get started with that butt plug and of course lots of lube.

A little begging from him to do with him as you will. :-[

Does he get to cum?
Will you make him beg first?
"Bring him/her to the edge is a fun game."

Course, after you've teased him silly, it would be nice to let him have some relief.