Boondocking Washing Machine (?)

I bought a Wonder Wash to use in between runs to the laundry mat. Much less expensive, but not worth it. It didn't do anything more than I would do if I just filled the sink with wash water, washed by hand and then rinsed. It used more water. I'd just use a sink or bathtub. I've read that a good way to do it is using a new/clean toilet plunger as your agitator working it up and down mixing the clothes around, in, out, like a washer would, then rinse, wring and hang to dry.