I feel like, with this question, you would get a lot of cocksuckers in on this thread.
I have not been in the video viewing areas of an adult bookstore, or anywhere where there is a gloryhole, but I have looked around for them, and if I found one, and committed to it, I would suck every cock that came through that hole, or holes (except the really STD looking ones). So, the 7" cock going through that hole? That's #13 for me. When I walk out of that booth, or stall, or whatever, my clothes are going to be made out of 50 percent cotton, and 50 percent cum.