Walter, I nearly choked on my breakfast when I read your reference to Persil. I'm married to a German and on my first visit to meet the then girlfriend and possible future in-laws, I needed some laundry done. Down to the cellar I went with my girlfriends mother to be greeted with a 50 year old washing machine, which while it worked it was seriously ill.
Persil saved the day, my mother in-law who doesn't speak a word of English and I didn't really speak German, mimed what to do pulling a bucket of soap powder in a cupboard. The method she used was a long soak in the powder/water, then into the washing machine with a small amount of powder then two hours later the whole house reverberated to the sound of the spin cycle. They were so clean I couldn't believe it, I was then shown the secret, Persil. Which is a German invention.
To answer your question, I often wear those trousers that one can take the bottom off and turn them into shorts. This I did as they were seriously muddy. Fortunately I was in the truck, which has a camper bolted onto the tray, plus we have a 140 litre spare tank of water under the tray. I rinsed them outside under the truck, then I went inside and got some water, some washing powder, then placed it into my around the world travelling washing machine; worked a treat. I hung the washing on a line inside the box under the bed of the camper.https://thescrubba.com.au/products/scrubba-wash-bag
The Scrubba washing machine really does work, I've used it in various parts of Australia, especially where water is really scarce, Iceland where we spent 2 months, saved a motsa on potential washing costs. The only time I used it in Germany was with my brother in-law at the bottom of his garden in June where a stream passes. I used the water from the stream to wash the same trousers I was wearing for the above picture. He was very impressed, but also amused at the effort I went to to have clean clothes as we travelled.
The mud on my shoes though, is another story.