How to intergrate two flocks?

[Summer98]

I have two separate flocks of free range chickens. They all get locked into their coops overnight and take turns every other day being outside to free range. I would like to get to the point where both coops free range at the same time. So that means they would "meet" for the first time while free ranging. They are currently trained to go back into their own coops. How do I go about this? I'm not worried about the hens interacting, but I am worried about the two roosters meeting the rooster from the other flock. I also have my "favorite" rooster, whom I don't want to get hurt. Do I just let them out one day and let them discover each other? If it went well, I would consider placing them all together in one coop eventually.