I much prefer making a zinfandel by hand rather than a merlot. The grapes are much larger, so the number of grapes we had to pull off the stems is much lower. The year I made the merlot by myself it took me from 10am to 1am with a 30 minute dinner break to harvest the grapes and pull them off of the stems. (I'll do the math for you. It took 14.5 hours.) It took the two of us three hours to harvest the grapes and pull them all off of the stems.
It was divine providence that I managed to get a hold of Dennis and harvest the grapes when I did. The next day it rained. I heard on the news that all the wineries in the area were scrambling to harvest. Partially because the grapes would rot from the dampness, but mostly because the rain would drop the sugar content in the grapes. The higher the sugar content is, the more food the yeast can use to make alcohol. Low sugar content makes for watery wine.
I mashed up the grapes on my own when I got home. I used my hands, not my feet. Everyone wonders. My brother commented that I ought to have a cleaner hobby.