Advice :)

Hello, I wanted some advice from someone on this.So, I'm openly gay. I would like to flirt with guys, but I'm not really into the so called "gay scene". I hang out where everyone hangs out. I'm a straight acting man as so many other guys. I know there's times when it's hard to distinguish if a person is gay and I have let go a lot of opportunities by also me not saying or revealing that I'm gay. When I get close to someone I always try to Start a conversation but obviously I'm not gonna be like hey I'm gay let's go out or hey are you gay?So, my question is how can I let someone know I'm gay without making them feel awkward or just spark an interest on them..Last week I was at the train going home and this other guy was kinda like staring at me. The train made its stop and he went down as he went out he turn his head and we started staring at each other. Sadly no one made the move but I would've done something if I knew he was gay or maybe he didn't know I was gay. It's always that fear of being rejected especially if it's in front of people, what if this person reacts. I don't know haha but I wish there was an easy way...