We have a whole routine now, and even Melody does a good enough job I don’t have to re-do hers.
We start with sleeves up and water in the sink. The girls get their hands wet and are alloted soap by a grown-up (many incidents have reinforced this is the way to go). Soap is placed out of reach if children are left alone to finish, most of the time now.
The girls rub as fast as they can, “to make bubbles” everywhere. Maybe when they’re older we’ll introduce a song for length, but this works for now. Then they rinse in the sink again.
There’s usually still bubbles on their hands, so they’ll often get a second rinse, but either way this system uses less water (by my uneducated calculations) and gets the girls doing their own washing up (formerly one of my least-favorite activities, for whatever reason). Both useful features.