Here's an interesting link, for those who like to watch a guy being masturbated to an excellent cum. She uses a cord to tie the base of his erect penis, and the shaft - very erotic! I've used this method of tying while masturbating, though I use a slightly heavier nylon cord and I don't wrap my shaft, only the base of my whole package, my testicles, and the base of my penis. I can tell you that it's very powerfully erotic to experience.
Be warned - the video is over 30 min long, so if to want to watch from beginning to end, you'll have to have immense control. I love it that we can see her tits throughout the video. I wish we could see her whole face, and I wish she had allowed him to cum onto her tits. But it's still worth viewing this. Several other videos nearby this one.
http://www.pornhub.com/view_video.php?viewkey=ph5753f40a90d84