I have learned to trust my gaydar. Many people say, they are straight, and if my gaydar confirms that, I simply move on. See, I would not want to have sex with a woman, and he probably feels the same way about having sex with another man. He is into a totally different hardware and that must be completely respected, no matter what. A no go is a no go.
If my gaydar says that the dude is untruthful and that there is some scope for action there, I go by the rule that everyone above the age of consent is a fair game.
Some straight men would not mind sucking a good dick on the condition of total discretion. If he perceives you as absolutely trustworthy and not compromised in his hetero world sense, you have a good chance of jumping his bones and with some luck, you may end up having a FB of a kind.
Some straight dudes need some sort of excuse to go down on you. Everyone is different at that, too. A number of guys belong to the 'six-pack, plus one thing led to another rule' and they are at it without much ado. The others need something more substantial to get in touch with their gay or bi side. If you are good at it, you'll soon discover the object of his desire. Give him what he wants, and he'll oblige, now that he has some sort of an alibi.
A number of straight guys are straight alright, but insatiably curious. (They also want to get their rocks off without much ado.) If you take the 'experimentation approach, making sure that no one else will ever know and that no one is under any obligation to keep on experimenting, unless they want to, little miracles will happen.
However, when it comes to guys, who claim, they are straight and all, but send mixed signals and would give it a try, nothing than the assurance of absolute discretion is more important. Being very open about your sexual life in general, or even with him is usually very counterproductive here. Keep it very private in general, and he'll quickly assume that you won't treat your affair with him in any other way either.
"And, when you want something, all the universe conspires in helping you to achieve it." - Paulo Coelho, The Alchemist
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