Getting that effect to work just right

Somehow, I know that this is going to be a lot easier than I’m making it out to be, but after playing around with it for a couple days off and on, I’m about worn out on it.

OK, here’s the effect I’m trying to get – I’m trying to make my menu appear as if from behind some clouds, like the words were hiding behind the clouds until a gust of wind blew the cloud aside, revealing the words.

I’ve been playing with a mask effect to try to make it work, along with some transparent clouds on other layers, but (1) you can’t tween the mask, so you have to make the button move, which isn’t what I wanted, and (2) I want the button to make the gradual fadein from left to right as the clouds pass over them, but when I alpha it, it’s going to affect the whole button immediately which, again, isn’t at all the look I’m aiming for. All round, it comes out looking kinda crappy.

Anyone have any suggestions, or know of any tutorials for how this effect might be best pulled off?