Men don't often have a lot going on in their heads. They barely focus on anything that doesn't directly deal with them, wrapped up
doing whatever they need to do in their own world. That only makes them a better target for conditioning, empty vessels receptive to any subconscious message around them.
It's only a matter of constantly bombarding them with images of altered masculinity in their peripheral vision- men with beards, men in the gym, dumb obedient men with no purpose. They begin to accept that's what they're meant to be, their focus working on molding themselves into the new picture in their mind.
Each time they look in the mirror they grow closer to that appearance, having let their bodies grow hirsute, having a long beard descending from their face. Their figures are transformed into a temple of muscle, taking time in the gym to grow defined shoulders and arms, their muscled chests covered in hair that they'd shaved from their head. Soon they're just another vacant slave to society, willing and able to work any job that's required of them.