You shouldn't need to mix up so much. My procedure is to mix up a couple of litres in a fermenter, seal, and give it a good shake every now and then. I also run some through the tap, tap threads and lid thread. When I'm ready to fill the fermenter, I just empty it and let it stand upside down for a few minutes. No rinsing needed. (Of course if you thoroughly clean everything after use, you're almost there anyway.)
I also have a small sprayer filled with solution for surfaces, hands etc.