First off, he is a lucky guy :)
Well I would say you should encourage him to try on his own first, just to see how he feels about having something tiny up his ass (his finger). Then make sure you tell him to have enema before you try it together so he doesn’t feel uncomfortable having you finger him. Last tell him to watch my blog as a proof that’s the strongest orgasm he’ll ever have :)
Keep me posted!
Very likely