..............
So, you know they have claws (as do cats) .... it's simply a matter of learning to handle them (as you do with cats).
First, why do you need to grab the bird? Muscovy generally herd well if you go about it the right way. Keep 'em on the ground under their own power, find yourself a nice long duck herding stick and move 'em as much as possible with it.
If you do have to carry a drake, wear gloves and leave the feet alone as much as possible. That is the only time I don't support the feet of a bird I'm carrying is when I carry drakes. (I like to support feet as it makes them feel more safe and secure and usually helps keep them calmer). I simply grab the wing near the body, one in each hand, and hold the bird as close to my body as I can. He'll flap a bit but by holding the joint he doesn't get much momentum and can't do much damage as he could if a wing got loose while you were carrying him around his body. I do this rarely as I move my birds on the ground as much as possible.
If you do want to hold the bird close to your body grab the feet and fold them together so that all of his toes are held together and wrap the foot around your hand. They can't do near as much digging with their feet held like this and it's less likely he'll accidentally scratch you. That's the key, I have yet to see a Muscovy attack a person with his claws intentionally. The claws are there to help with perching, not attacking. They're pretty much just present at the end of his toes and any scratch you get is a result of him trying to get away not so much trying to kill you.
This photo shows my niece holding a duck with the feet folded like I mentioned. I'm a fairly large (5'10") stout person and could not carry a drake like this where you use your arm to keep the wings pinned to the bird's side w/out having to use another hand.
FWIW ... I do not use gloves as a general rule as I dislike the loss of mobility but by all means, use gloves if you need to.