I have a rescued muscovy drake who started attacking me from behind at the beginning of his second year. I read the advice and did the pinning down. it was awful and it did no good. My drake was stirred up by male hormone surges on top of his prior experience that left him near drowned as a little fluffy and needing rescuing. I hated the pinning down more than he apparently did, and so I tried picking him up and holding him until he had settled down. He hates being handled!! When I didn't have time to pick him up and wait for calm, I took him and dropped him in our wading pool. He hates water!! I used the picking up, and dropping him in water, during his third year, and less frequently in his fourth year. He is now in his fifth year and hasn't as yet attacked me once. He is like all my boys, he follows me round when I am in the back yard, telling me all about it. He comes when I call from the gate or patio door. He waits for me by the garden gate at bedtime. When I am cuddling my one cuddly drake, he is right there watching, just out of easy touching reach, telling me all about it.
I think he has over the years just grown out of attacking me. Carrying him until he calmed down, and dropping him in water made no difference to his behavior. I just felt better about carrying him than pinning him down. I definitely felt better about dropping him in water!!!!
So, I counsel against pinning down. You might carry a pool noodle to ward off attacks -- whacking with a pool noodle wont hurt him, but will stop an attack if waved right in front of his advancing face. Respond to him as you feel comfortable: picking up if you are able and have time, or dropping him in your wading pool. I have also picked up my boy and left him stood on top of a round concrete picnic table in the back yard. He was too shocked to know how to get down!!! And take heart from knowing that this behavior will taper off around August--sooner if you are lucky--as his hormones cool down.
I have a second drake that bites me every spring [this is his fifth spring]. I rescued him probably the day after he hatched -- he was found alone, running around a parking lot, in the dark, in a rainstorm, in danger of being washed down a storm drain. He came to me the next day almost dead. I hand raised him and I wasn't able to get other ducklings of appropriate size to keep him company until he was 6 weeks old. So, he is tightly bonded with me. He thinks he should live in the house and not in the coop with ducks!! He takes every and any opportunity to try and sneak in the house. And every spring he starts biting me. It's not an attack from behind. He will often flatten himself in front of me, and then come and bite me. He doesn't actually try and mate me. But he's demanding attention. I try to give him 5 minutes every day sitting down on a step with him at my side having a cuddle. He is blissfully happy with that. when I am busy, and it's not cuddle time, I have to walk with a stick to keep him from biting my shins and calves. He is NOT intimidated by a pool noodle. He likes being picked up, so that doesn't help, and he loves baths, so dropping him in the wading pool doesn't work as he just comes straight back and tries to bite me again. The only thing that works with that boy is a stout stick waved directly in front of his face!! I will not ever try pinning him down, but I suspect he would like it: at this time of year, he often flattens himself and shakes his tail feathers in front of me, prior to trying to bite me!! It's definitely his drake hormones giving him [and me] trouble. So as
@KathiQuacks advised, there is no one way of managing drake biting. What works varies with the drake and with what the duck-mama/papa is comfortable with