Depending on the severity of their situation, they may require veterinary care at first. In the hospital, I use the following guidelines for how to start feeding a starved dog...
First, it's important to be sure dehydration is adequately corrected before starting food. That usually requires IV fluids. Otherwise, feeding a dehydrated animal (or with electrolytes and acid base abnormalities) can be problematic.
Next, I use the dog's current weight to calculate their RER (resting energy requirement - in kcalories). I'm usually pretty conservative, to try and prevent problems related to volume intolerance (vomiting, nausea) or refeeding syndrome (metabolic abnormalitites associated with refeeding). We do not have good predictors of which patients will show these problems, so it is impossible to say how important is slow reintroduction in this case.
I usually give only 25% of RER first day, so it takes me 4 days to reach full RER. Closely monitor for any signs of food intolerance (nausea, vomiting, weakness).
The goal is to initially stabilize her weight, and then re-gain. Once you are at full RER for a couple of days and the dog is doing well, I would increase the amount fed by 10-15% weekly. Once you reach the desired body weight, start decreasing the amount of kcal fed by 5-10% to prevent further weight gain. Once she is weight stable at the weight you would like her to be, the kcal needed for that is her true maintenance.
I would probably use a lower fat diet (fat is usually very digestible but it is the most complicated nutrient to digest).
I know this all sounds very complicated, and I can help you sort through it when you return online.
I'll be going offline for the evening myself shortly, but will be notified of any response via email.