I am a small person right at 5 feet tall, maybe 100 pounds. That said, I also have 3 ganders. A very big Embden, and 2 chinese. All 3 boys have learned its not smart to cross me. Its best to use the natural language they understand, pinning the opposing "goose". It is not cruel, its teaching them in their own language whats not ok.
You have to remind yourself you are bigger than they are. When they charge, I grab the neck firmly with one hand just below the head, pulling him towards me, my other arm goes around those wings. Get those wings, they hurt! Down we go! I pin the gander down to the ground. I try to hold with my legs in case anyone else tries to get in on the fight. Once he stops struggling I release him, I do not let go of that neck until then. Hold out your arms, scolding him loudly and make him walk away. thats the "victory dance" once you have won the "gander fight" and exactly how they do it. Usually once is enough, sometimes you need a repeat, like my Big Boy Embden. He is a massive bird, very territorial and fiercely protective of his goose hens. I have been pinched a couple times pinning him, but he has to know its not ok to attack me. Once you establish your pecking order in the flock it should stop. Its really no different that teaching a puppy to not bite or scratch you.
Other people use large plastic garden rakes to scare them, but its just putting a band aid on the problem. Successfully keeping geese means being able to control gander behavior. It is intimidating to see that charge towards you! Hopefully other members can offer ideas as well.