Maintain your cool. There's not really a formula for flirting. You don't try to be sexy, sexy just happens. Keep your glance for at least a few seconds after you've locked eyes. He could flirt with gay men and not be out of his comfort zone, but he is attracted to women.
Chill out! People have to develop their own way of showing they are interested in someone else. I call them "gay" for flirting with me, and not wanting anything sexual. So always make sure you are open to reading the other person's signs and if they don't seem interested, try hard not to feel rejected, and do your best to move on.
Neither should you.