There's nothing wrong with a bucket! Although it is time-consuming.
Have you seen you can get little mini portable washers?
Or even more simple you can get these things that look like plungers so you don't have to get wrinkly hands, should be good for travelling. I've always wanted to see how well they work.
I'm clearly a lundry geek, I also just noticed this quite cool contraption, it's a backback but also a sort of sealable dry bag with a textured inner surface that doubles as a laundry bag for travel hand-washing.
Brilliant! I hand washed for 10 years as no machine and not enough power, then upgraded to a 100watt campervan wash machine that ran on my small solar system, big pot of water heats up on the wood stove and i chuck it in and it washes great! love your post, will follow...