This topic isn't normally an interest of mine, but I came across this particular video while looking for something else. It's extremely arousing. It shows dozens of women swallowing cum, sometimes very large multiple loads, while a voice over encourages you to masturbate and swallow your own. It was very pleasant to jo to this one. I didn't allow myself to cum, but I can see how, if a guy were into swallowing, it might be impossible to avoid losing it while watching and listening.
http://www.xvideos.com/video2673584/eat_your_cum_little_faggot_with_audio