To be perfectly honest, most wildlife "rehabilitation" books & guides are not designed to actually save lives, they're designed to end them. It's a fact, albeit a sad one.
First and foremost, if you have a pet nursing bottle, throw it away. It will NOT work for your squirrel- what it WILL do is cause them to aspirate formula and give them pneumonia (which is essentially SLOW drowning).
You'll need a 1 ml Syringe
1 c. Whole Cow's Milk (yup, straight from the gallon in the fridge, and don't use that nasty low fat or 1% stuff!!)
4 drops of Vitamin E (from a 200 IU capsule)
Scald the milk- if you're not familiar with this term it means to heat the milk just to boiling point but do NOT boil it!. Remove from heat, add the vitamin E, mix with the handle of a wooden spoon.
You can also scald milk in the microwave. Measure 1/3 c. of milk into a mason jar (uncovered) heat on high for 25 seconds, stir with wooden spoon, heat additional 25-30 seconds or until milk starts to appear a bit frothy. An easier way to tell whether the milk is properly scalded is that begins to form a thin skin on it from
Feed warm formula every 4 hours, round the clock. Do not skip nighttime feedings as your baby critter will die. Do not feed a cold animal- if you just found an orphaned baby critter, be sure the animal is warm BEFORE you feed it or it will be unable to digest the food and will die. Place a towel over a heating pad and gently & slowly warm the critter before feeding.