I know this may be cheesy but it has helped so much!
Hailey has decided she is old enough to wash herself in the bath but due to her young age she never really quite cleans everywhere. So I have started to tell her she needs to cover herself with soap and be as white as a snowman. I bought her her own fluffy sponges and when she is done cleaning herself all over with soap, we sing "Once there was a snowman, snowman, snowman, once there was a snowman tall, tall, tall- in the bath she melted, melted, melted, in the bath she melted small, small, small" On the melted part, she melts into the water and rinses off.
Desperate times call for desperate measures-even if it is a little cheesy!