My boy is shy. NEVER drops when I'm near. Doesn't mean he doesn't get his bean taken care of, though it's a little tougher. Cleaning his sheath requires me to go elbow deep anyway, and if you've done that, you've noticed that his parts are all still there, even if you can't see them.
So, in your mind, imagine what your target looks like. Get a horse anatomy book if you must. Then go in there, grab the part, feel for the pocket in the end, and you'll run into the bean. Then gently coax it out. My guy gets wiggly when I do this, so I try to be quick as well as gentle. If you 'aim' wrong and wind up in the urethra, his eyes might get real big and he will probably object, but you won't have injured him so long as you are gentle and use plenty of Excalibur.
Of course, the very valid alternative is just to pay your vet to do it!