Are you into stuff like circle jerks or mutual masturbation? What's the best way to approach something like this?

I have enjoyed both. Its not the sort of thing you can announce when your out for the evening with your mates though (unless you know they'd be up for it). I've met guys in hotel spas where we've ended up wanking each other either in the steamroom, sauna or my room (and even once or twice in the jacuzzi). I've usually known within minutes whether a guy is up for it. The norm in the sauna or steamroom seems to be an open towel and a guy playing with his cock whilst looking at you. I usually take this as a sign he's interested and I'd open my towel so he can see my cock. if I'm not interested then I'd not do anything and the guy takes the hint.

Ask me anything