My daughter broke her wrist 2 different times.
My solution was she wore a bathing suit. I washed her hair and good arm. I then handed her a soaped up wash cloth and told her she could wash the rest.

Being a single dad I “knew” if there were ever any questions I would be the first one they would look at. So doing it that way protected me and made it less awkward the 2nd time when she was around 11 or 12.
Edit Oct 4 to add:
I was the only parent my daughter had since she was 16 months old. I did what was needed to be done with no questions and she knew she could believe me and count on me. So there was never any question about me “doing my job”.
That doesn’t change the fact that there are many cases where men are falsely accused of things and it destroys their lives even if later it turns out the accuser lied because they are considered quilty until proven innocent. The 4 Duke lacrosse players had their lives turned upside down and could have spent years in jail over a lie if there parents couldn’t have afforded tens of thousands of dollars in legal fees that never were paid back by either the liar or the prosecutor. If you are accused of molestation of a kid, which a number of women have done to “get their exes” it is even worst. So yes I was smart enough to be aware of that fact and to try to protect my selves.