I boondock camp high in the mountains for about 3 to 4 months of the year, so I do most of my laundry by hand. I like to pick an area for laundry that has a nice easy water source so I don't use my tank water. I fill my wash bag half or quarter full with water, and then carry it up away from the stream at least 200 yds.
I use a roll top dry bag for washing my laundry. I think mine is about a 20 or 30 liter bag. Here is a link to a 20L one that is like mine.
https://www.amazon.com/dp/B01ERK6R28/re ... th=1&psc=1 It is pretty tough and handles all my rough usage. To wash I just put clothes in, add soap (you only need a little, and I use biodegradable), and then I agitate it. I will sometimes roll it, rub or rock it with my foot while sitting in a chair, or even take it for a nice rough ride in the truck. Most anything works.
I usually agitate it for a few minutes then let it sit 20 min or so and come back and agitate it some more.... depends on how dirty stuff is. I might even rub out some stains by hand, but I seldom have to do that. Then I will drain it (a nice slope works well for this) and rinse a time or two. It is a bit of work, but not bad if I do it once a week or so. My camping wardrobe mostly consist of fast drying nylon or polyester.
I use a Nina Soft Spin Dryer which makes the whole process easier. It speeds up the drying process and makes draining and rinsing the clothes a lot easier. I spin the wash water out, and the rinses. Drying usually takes place on cords I string across my shower, or I may string a line between trees or between my truck and camper. Everything drys quickly after being spun out.