Aw, poor Tibbe

!! So sorry all this is going on for you both.
If the yeast is really systemic and wide spread, then you may very likely need a round of Diflucan or Nystatin x 14 days or even more. That would clear it up easily and quickly, and prevent further spread. Baths and topical stuff doesn't always work well w/ infections that have spread and are rapidly multiplying.
For shampoos, I'd probably go with either/both
Duoxo or one of these shampoos going forward, if there are ongoing skin issues:
http://smile.amazon.com/s/ref=nb_sb_...bs+vf++shampoo
"Hot spots" are actually staph intermedius infections (pyoderma) and can sometimes be treated topically/locally, like w/ Mupirocin from the vet.