I also got my cag at 4 weeks he is 18 weeks now. It is relitive easy to feed a grey they are fast learners and will start take the spoon as soon they find out where the food is coming from. Take a teaspoon and bend the front to form a 10mm channel in front.
Mix the formula so that it is about as thick as yogurt, it must run nicely off the spoon. Boil the water, let it cool down, then mix the formula, start with two tablespoons of formula and ad the water till it is right, mix very well, now heat it in the microwave a little and stir it very well cos the microwave make hotspots, be carefull if the formule is to hot it can caurse cropburn witch can be fatel, I taste it myself to make sure, check the temp with a thermometer, the feeding temp is 40-43 degC this is very important, otherwise the baby will refuse it, it might be necessary to heat it a couple of times as the formula cools down while feeding, add hot water if it gets too thick. Feed approx. 50 mills 4 times a day. Keep the baby warm a cold baby won't eat, to make sure feel the wingtips and feet if it is cold the baby is cold, a temp of about 25 degC is ok at 4 weeks then you can slowly reduce the temp to 20deg at 6 weeks. Then a lot of patients and love, after every feeding hold and cuddle him. The other important thing is to be very hygenic, rinse everything in a sterilisation liquid before using, wash wel after use, and before feeds check that his crop is emtying ok if there is still food in wait another hour before feeding, if the crop don't empty at all, there is a problem see the vet.
I hope you understand I'm not good with explaining. There is good sites if you Google "feeding my baby african grey" spend some time reading thru it.
Good luck