I have been going on the assumption that if I use the same meter all the time, all my film will be exposed in a similar fashion. That way if I do find major differences then there is a good chance that something with the camera (shutter), or lens (aperture) is working differently than I assume it would. That is if I am using the same film.
There are occasionally small differences between cameras using the same film but it is usually the differences between medium format (Rolleiflex) and 35mm (Pentax.)
I suspect that my assumptions are probably off but it has worked relatively well. I suppose it should be mentioned that there is always an exception to any rule of thumb.