Wash your armpits
You know the situation: the shower is over in three minutes, but the smell is still there because the arms never left the sides. The visual support below gives the armpit a step of its own, along with the movement it actually takes to reach it.
♀Wash the armpit
A girl raises one arm and washes her armpit with soapy foam.
♀Wash with a sponge
A girl holds up a dripping sponge and washes her armpit with soapy foam.
About this visual support
Armpits belong to the places that get skipped almost every time, and the reason is purely practical. You cannot reach one without lifting the arm properly, and that movement is not part of a fast shower where the hand simply sweeps over stomach and back. The result only shows up later in the day, often noticed by someone other than the child, which makes the reminder an awkward one to give.
That is why the step works better as a picture than as a comment. A card with a raised arm and soap shows both where and how, and the child can follow it without anyone mentioning smell or bodies. For children who are sensitive to touch or to the feel of soap, knowing in advance that this moment is coming and that it is short takes a lot of the sting out.
A practical tip: tie the soaping to a position rather than a time. Arm up when the child turns towards the wall, then the other arm. The movement becomes part of the shower instead of an extra task at the end. Routined lets you assemble the shower steps with pictures and a timer, with a 14 day trial period at no cost.