From: Philadelphia, PA
DO NOT use the elastrator bands. The folks that I know that play with them use them on nipples, not balls. (I've participated in the castration of farm animals and know what damage this does!)
Something I'd suggest as a mind fuck would involve icing the balls and drawing them back towards the buttocks as they get numb (or if you're into needle play, inject saline and tell him it's lidocaine to numb the scrotal sac so he can't feel it), a sharp implement being flashed, drizzling warm, sticky liquid (even microwaved lube works for the simulation of bleeding) as you "cut" an incision and pull on the numbed sac. Plunk something in a jar -- I'd go for some sort of animal gizzards or similar looking part. Go to town, making like you're suturing or stapling the hole. Apply a sterile dressing and close up his legs "to apply pressure."
The only drawback to this is that you really need to do alot of mental work before this practical application so he truly and honestly believes you're committed to doing this. Making him draw up a faux legal waiver or some sort of contract to you might be the right road to go down.
Ms World Leather 2004
Ms Philadelphia Leather 2004
"Simply put, if you want a real femdom to love you, give her reasons to love you." Gloria Brame