thats a good question... i guess practice makes perfect, take a couple of really seductive pics of yourself and give them to him to look at when he's "practicing"!

I have never heard of a guy not being able to jerk off before. I am sure he is fine. If his penis still works when you are tending to him than he is ok.
If he needs to cum in a cup why not go in the room with him and do it for him.

Hmm very odd. How does he get off when he's with you? Help him out and spit it in a cup for him

thats what i was about to say why dont you go down on him and wait till he comes and put in in the cup, kinda like the pull out method... just in a clinic... pus it could be pretty kinky... ever gone down on someone in a hospital office