Hi,
not tried it but - I would advise using an emollient thickly spread around the vulva , such as hydrmol, before washing which will protect the skin.
If there is dermatitis on the outside a short 3 week course of a ointment based steriod, will calm the area. Only a tiny ammount should be used with a mirror to see where you need to put it.
Then once the skin has calmed introduce 0.01% estriol cream just on the outside . Again a small peas size every other day or even once a week initially, until you feel comfortable that it wont cause irritation. then increase.
Vaginal atrophy is awful, but it can be improved, by paring back what you use.
Also go knickerless, that can help.
PMX