Another piece of advice I will share is to start young. My last batch of chicks from a hatchery included a BJG* cockerel. Starting at about a week and a half old, when I would clean their brooder, while the other chicks would huddle far away from me, he would run up and chest-bump my hand. About the third day he did this, I bumped him back, not hard. He ran at my hand and did it again, harder. I thumped him again. I didn't want to hurt him. This time he stepped back and charged at me, hard! Feeling I needed to nip this in the bud, and the sooner the better, I reluctantly thumped him back, convincingly. I didn't want this to continue. This time, he backed up and looked at my hand thoughtfully for a minute, and then walked away. The next day he charged me again, and I thumped him, hard. He backed off. The third day he ran toward me, and I thought we were going to have another repeat, but he stopped himself and just looked at my hand, then walked away. He is over a year old now and has never shown another sign of aggression.
*Black Jersey Giant. The rooster that hurt me was a barnyard mix of primarily EE extraction. I knew George would be much bigger when grown, and I certainly didn't want any aggression issues with him once he reached full size.