Can I use AE shift to adjust the brightness of a GL1 so that it will match another GL1?

I have 2 GL1's and a GL2 that are used exclusively for weddings. The image for the GL1s do not match satisfactorily. GL1 no. 1 is brighter than GL1 no. 2. About a year ago Canon replaced the CCD assempbly on GL1 no. 1, and I think that is the reason it is brighter.

I've been working with the camera operators that use the GL1's to try and match the image better. We use Auto on all three cameras: manual is just not an option for these operators. During a wedding last weekend all three cameras matched very well by using -2 to -4 for the exposure lock on the brighter GL1. (I use custom present to match the GL2 to the GL1's).

However, using exposure lock means the operator has to fiddle with the exposure lock depending on what light the camera is pointed into, e.g. up the aisle for processional or at the areas the vows take place.

Could we use AE shift instead? I read the manual and AE shift can be adjusted in .25 increments between +2 and -2. In your experience, how much should AE shift be adjusted to simulate a -2 or -3 exposure lock adjustment?

Does anyone have experience using AE shift that can help me out with this question. I'm a little surprised to get no responses. Maybe everyone else is using all manual settings.

That just is not an option for my camera operators. They are great for framing shots and following the action of a wedding. But adjusting f-stops and shutter speeds during a fast moving wedding that moves through two or three lighting situations on the fly would be too difficult, and in my opinion, not very successful.