Look for massage adds showing hot girls. Usually, there will be a towel there but the will not tell you to use it. If they come in with your ass covered then they know you just want a massage. If you a naked laying on your stomach with your legs kinda spread apart they know you want to be masterbated at the end. If they ask if there is any particular part of your body that you want massaged, tell them your ass and upper legs. As she gets to your legs and ass, arch your ass up a bit to signal to her that you want your testicals massaged. If she brushes you testicals or anus, tell her how good that feels. Torward the end she will ask you to flip. If she is still unsure she will ask if there is anything else you want massaged, at that point tell her you want release.
That works for me anyway.
