Well, I do believe you. At times I can hear things too. But I'm really working on getting it out. And the education, harmony etc, is really helpfull for that. And it helps in other ways too. Sometimes I write a piece, but just run into a dead end, and then you can release the theory on it, and it will guide you to a solution.
But for a real orchestration, you do need to know what the different instruments and there capabilities are... (I was thinking orchestration as in a piano concerto or something like that. I think you're talking orchestration in non-classical music, right? Otherwise you're truly a genius...)