Grapes are so dirty, especially red ones IME. I cut the large bunches into small bunches, then spray fruit and veggie wash directly on the grapes, move them gently around in the bowl, then cover with water and swish for a minute, drain, cover with rinse water, swish, and drain. It only takes a minute.
By the time I'm finished, the water is clear. For other things like berries I just spray some f & v wash in the water, but grapes get special treatment because they are just so dirty.