tell him to read mantak chia's book cultivating male sexual energy, then if he is serious in studying the techniques in there, then to seek a teacher
get dat shit fo free right here!! http://www.slideshare.net/guestcaaa41a/mantak-chia-taoist-secrets-of-love-cultivating-male-sexual-energy-328-pages
Maybe it is the desire to have Sex and not make Love which is the problem (?!?) It may be the (frustrated) intent which sees disappointment (?!?) Try going with the intent for Passionate Love - right up to, then stopping short of sex. After a period of regular physical interaction and without the pressure to gain a climax of conclusion, there will be a the time is such that such will arrive naturally as a surprising 'bonus. - Persistence is never futile