Montana has some great suggestions. Only one thing I'd like to add. As you push him to the ground, pinch the skin on the back of his neck. That's a hold an alpha rooster would do to another roo to show him who's boss.
Never show fear! The more contact you have with this rooster, the more he will get used to your dominance over him. I have a six-month old roo that I've been making a point of handling in a dominant way every day since I figured out he was going to be a roo. He doesn't like his daily attitude adjustments much at all, and he goes out of his way to avoid me. It's the best possible relationship you could hope to have with a rooster.
Never show fear! The more contact you have with this rooster, the more he will get used to your dominance over him. I have a six-month old roo that I've been making a point of handling in a dominant way every day since I figured out he was going to be a roo. He doesn't like his daily attitude adjustments much at all, and he goes out of his way to avoid me. It's the best possible relationship you could hope to have with a rooster.