Getting proper exposure when shooting a multiple exposure shot
I've been playing around with the multiple exposure mode of my Hexar AF, but I was hoping I could get some clarity on how to manage a properly exposed final shot. I ran across a comment on another website that said one way to achieve this is to manually change the film speed rating, so, for example, if I was shooting 100 speed film and I wanted to "expose" the frame 4 times, I would manually set the film speed to 400 then after I take the 4 shots I would have a correctly exposed photo.
Is this correct? Am I misunderstanding something? Is there a better/faster way to go about this? I'm just playing around really, experimenting, but I would rather if all my photos didn't turn out extremely overexposed.
Thanks in advance,
Deuteronomy 23:1 --He that is wounded in the stones, or hath his privy member cut off, shall not enter into the congregation of the Lord.