Use hot water to remove most of the crap and then shove a microfiber towel, washcloth size or so, down the hole. Put enough hot water in so the towel will swirl around in there while you swirl the water. Cleans off the gunk in only a few minutes. Sanatize and you're ready for the next batch. No soaking or scrubbing with a brush. The only yeast I've had to soak was Pacman....for some reason that yeast sticks like crazy. Otherwise the microfiber towl trick works everytime.
Found the idea on a you tube video.