After returning home, I reviewed several web sites that offered helpful information on how to harvest elderberries and remove the stems; here's one that provided options on how to de-stem the fruit. I elected to leisurely tease the fruit off the stems with a wide-toothed comb while enjoying a movie.
I found it easier and more productive to tease off a small number of berries instead of trying to rake off too many berries at once. The fruit gets damaged and stems end up breaking off as well. Next time I harvest, I plan to dry and freeze some berries before de-stemming to find out if that makes the process quicker or easier. I netted three gallons of fruit weighing in at about 16 pounds once the stems were removed. It took about 6 hours all told to remove the stems and wash the fruit.
I put about one gallons of berries in the freezer, one gallon went in the dehydrator, and the third gallon went into a pot to juice. The dehydrated gallon of berries weighed just over five pounds wet and about one pound dry. I also plan to use the elderberry juice to make mead, but that's a tale for another time :-)