I've worked as a squirrel rehabber since around 1998 for WRANPS in South MS. Squirrels should be fed puppy replacer(we use Esbilac).HOWEVER,if you have already started with a kitten replacer,DO NOT CHANGE!..Their eyes generally begin to open around 3-4 weeks of age.They should be kept at a good constant heat source(the bator is good.just be sure there is good ventilation.) Be sure not to over feed themThis can cause problems. Watch for any signs of milk aspirating from the nose.This is not a good sign.It shows that milk is going into the lungs and can cause aspiration pneumonia. Lots of times babies can seem to go rather 'catatonic' while nursing,stop the nursing until the baby has regained his senses. once the feeding is done be sure to help the baby eliminate himself.Simply wipe it with a warm cloth until it urinates/deficates. Watch for diarrhea always bad in any species.Do not use towels for bedding.Use old T shirts or something similar.Towels can cause the babies to get their toes caught and cut of circulation.Usually the babies begin to fluff out around 3 weeks the incisors start to protrude around 3-4 weeks and the tail becomes bushy around 4-5 weeks. Once the eyes open,you can begin to offer solids.try bread,cheerios,or rodent chow if you can find it soaked in the milk. You can also offer some fruits.Avoid things with lots of acid(such as grapes) as it will upset their stomachs and cause bowel issues.Around 5-6 weeks they will need a larger cage with branches and stuff to climb and gnaw on. You can start giving them a variety of nuts(not just peanuts) and be sure they are fresh,not cooked/salted.Be sure they have a good variety of natural foods.Rodent block,monkey chow,Zupreem biscuits,cheerios,fruits and nuts.( Flying squirrels in the wild have a diet mainly consisting of bugs and stuff.So for flyers you would also need to be sure to have thm some crickets,etc as they require extra protien) By 6-7 weeks they are usually fully weaned,by 8 weeks should definately be.Be sure they have good sources of calcium also,as squirrels tend to have issues with MBD (meatbolic bone disease) which is a calcium deficiency.Once they have good teeth start giving them whole nuts to crack themselves.It promotes their natural learning and provides the neccesary hard surfaces to keep their teeth filed down.Their incisors grow continuosly so their natural instinct is to gnaw to keep them filed down.