Any photos yet??? That would help....Karla
I don't know how you ended up with this poor puppy but hope you aren't just keeping some person in business.
That being said, glad you have a Vet appt on Friday so at least you are doing the right thing. Please make sure the pup gets a full series of shots and I don't recommend taking it out to public places as there is a risk of Parvo.
She was probably on a poor diet. What are you feeding? Try a grain free food with Omega 3in it.
You can bath in an oatmeal shampoo that is made for dogs. If there are no open sores, you can rinse with diluted Apple Cider vinegar, about 1part vinegar to 2parts water. Let that sit fir a few minutes and rinse well. Do not do this near the face. Do it from the back of the neck down.
Show the areas of irritation to the Vet who may want to do a skin scraping to check for mites.
Make sure you take in a fresh stool sample with you to be checked for parasites. The Vet should give you worming meds too.
Goid luck and keep us posted..