This is a scenario I could see myself in at some point. I'd say just be patient. If he's truly a friend of many years, it may take a while longer to get him. Keep dropping the hints but not pushing too hard. Maybe eventually he will be the one doing the pushing. What kinds of comments? Fake-gay locker room jokes, in a general sense? Pro-bi/gay comments, in a general sense? Commenting on how other specific guys look? Commenting on you or your body specifically? Peeing with the shower door open?
Do your shared activities lend yourself to sexual talk, or porn viewing, or locker room/gym type nudity? All these could be avenues, but he has to be willing. You are my age ... drop a hint about how things were so repressed when we were young men, and younger guys are lucky that they get to explore their sexuality more than you did ... maybe even tell him you feel like you have some catching up to do?
Hell, most of my stories are various ideas about how to "cross the line" from friendship or buddyship to sucking each other. Sex talk about your experiences with women, talking about (or better yet, viewing) porn, gym locker rooms, saunas, hot tubs, pools, camping. Again, I'd say keep exploring these scenarios. Don't push too hard, but keep giving him opportunities. He probably has multiple psychological barriers to getting cocks-out with another guy, and eventually he may overcome those once he realizes there's nothing wrong with it and that you want him too. Good luck.