My constant struggle is to "learn" a B&W "eye".

Sometimes it's easy - like when you see a bright sun shining through the slats of a deteriorating old barn roof onto a dark interior floor.

But that's "so obvious". A typical example of contrast and light extremes.

I think you're onto something by carrying two cameras, one with color and one with B&W. I often do the same - but really have to be more disciplined about doing side-by-side shots in each format.

Maybe that would help?