Controlling exposure on Yashica GSN

I have two Yashica GSN range finder cameras that I really enjoy shooting with. These were my first rangefinders. One was purchased for extra parts but was in such good working condition, albeit a bit ugly, that it didn't make sense to cannibalize it so it stays in the car or in a backpack with me all the time. All it took to get both up and running was new light seals that took less than an hour to install.

The auto exposure works very well for most of the situations that I photograph in but there are times where I have wanted a bit more control. While looking on Ebay for a new rangefinder that has manual control capability (and parallax compensation) I started thinking about how I might trick this camera into giving me the exposure I wanted. If I were to simply adjust the ASA dial a step in either direction it should fool the auto exposure into giving me what I want. For example, if I'm shooting 400 speed film and wanted another stop of exposure I would simply change the ASA dial to 200, in theory...

Does this sound reasonable? Am I on the right track here or am I simply going to waste a lot of film trying to get this right? It looks right to me but then I'm just now starting to develop my own film and make my own prints. I've shot photos for years but didn't realize until recently how little I understood about exposure. (Kind of like my first music theory class in college, I thought I knew about music until I discovered how very limited my understanding was!)

Any one tried playing with the ASA dial to get more control of your automatic camera? Any one have thoughts on this at all?

Thanks

Jeremiah