Being a believer in X inherently means, for a rationalist, that you think there are no good arguments against X. So this should be impossible, except by deliberately including arguments that are, to the best of your knowledge, flawed. I might be able to imitate a homeopath, but I can't imitate a rational, educated, homeopath, because if I thought there was such a thing I would be a homeopath.

Yes, a lot of people extoll the virtues of doing this. But a lot of people aren't rational, and don't believe X on the basis of arguments in the first place. If so, then producing good arguments against X are logically possible, and may even be helpful.

(There's another possibility: where you are weighing things and the other side weighs them differently from you. But that's technically just a subcase--you still think the other side's weights are incorrect--and I still couldn't use it to imitate a creationist or flat-earther.)