Speaking from my own experience, being direct truly is the best route. I am oblivious to normal flirting and signals. I have to be told point-blank. And from what I'm told, I am rather inscrutable even when I think I am expressing interest. I've been in a similar situation with a long-time friend, and I assumed that, if she had been interested, she would have said so long before. Even though I was definitely interested, I put that aside because I was convinced she did not reciprocate. I only found out later that I had missed my chance.
If you have been friends for some time, he is presumably used to you being outgoing and forward, and so you probably aren't going to scare him by being direct.