You haven't really mentioned what *you* want to do - do you want to perform oral sex? Only proceed with what you are comfortable with, and that goes for having oral sex in general and your gag reflex, if you do. Pornography isn't reality, and going beyond your comfort zone isn't much fun if you end up throwing up or gagging!
As far as sprays go, the only ones I can think of are numbing sprays for sore throats, and those will also numb your partner - of course, he should be wearing a condom, which would prevent it. However, using sprays to overcome something that is set up to protect you isn't a good idea. Instead, if you do decide to have oral sex, simply go as far as you're comfortable with. In the meantime, I would ask you to ask yourself if you want this as well - your desire (or possible lack of) is just as important as your partners, okay?
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