I have had the best luck with a father/son, whereas the son is raised up in the flock. So I would suggest getting him in there when you add the pullets. The older rooster for the most part should just ignore all of the youngsters. I have had much better luck with father/son, or older/young roosters than with roosters the same age.
But roosters are a crap shoot, and often times work, then don't work.
Mrs K
But roosters are a crap shoot, and often times work, then don't work.
Mrs K