Thanks, Deb!
The most useful thing to me about working with a professional bra fitter was her knowledge of brands and styles. Trial and error suggests that some brands/styles envision, say, a 32D as a wider, more rounded cup, while others offer more "depth" (and therefore on me can look pointy and leave some extra space in the front of the cup.)
Even after you know what size you should wear, it's a project to figure out which bra in that size best suits your particular shape.
I will also add that it's a project worth doing since nothing ruins the look of an outfit faster than the wrong bra.