I'm a designated suck buddy for several guys. I suck dick soo good they get hooked and beg me. Since I'm married, I don't have time to get out that often. My wife knows I love dick but don't wanna hear about it.
One thing I know for sure is, you guys gotta just be open and speak what you want. Also you can tell when a guy would let you suck his dick or wants to suck. They give you a certain look that you need to recognize. Once you do, you can just say, hey I wanna suck you and they will say ok, where at?
Trust me, most guys would let a guy blow them, its just about being discreet.