How to prevent biting? Rat muzzle?

I volunteer with a rescue and have offered to work with a highly aggressive rat that they have. He's so aggressive that he'll seek you out to bite you, he bites multiple times in succession if he can. It's testesterone-related, supposedly.

He's getting neutered next week and I offered to look after him. I also offered to work with him behaviorally since I'm experienced with unfriendly rats, however he is by far the most aggressive I've ever seen. None of the regular precautions work with him, and he's bitten me a couple times now after I fed him.

To make him safe to work with, because he'll have to be handled if there's any hope of getting him adopted, I need to find some way to prevent biting. Any ideas? A rat muzzle seems a bit cruel but it's all I can think of.