I started out insisting DD (2.5 yrs) washed hands after every visit - good hygiene, habit to train her into, etc. Good intentions have waned rather over months and now I have a newborn too and no time..
She does her businees on potty and doesn't come into any contact with bodily fluids as I wipe her afterwards. She generally wanders off while I am cleaning out potty. I am doing well if she pulls up pants rather than taking chance to remove them! I DO wash my hands of course.
Public toilets where she holds on to seat are a whole other story...