Feed with long tongs to avoid him thinking of you as the food source, but I'm with Jackal, a hissing, tail whipping aggro monitor = healthy and well adjusted.

My blackthroats are pretty irritable, and I'm happy to be able to feed them while being careful. I worry if they are too docile seeming, honestly.

If that "bathtub trick" is the one I'm thinking of, please don't use it. Nearly drowning a animal to "tame" it is dangerous to the lizard and cruel as well.