Spoons: I’ve got three orphaned babies right now myself!
She is still too young to wean. Don’t even try until she is about 4.5 weeks old. You are feeding her KMR or Just Born, right? A homemade concoction (recipes available at www.kittenrescue.org) is okay for a temporary solution, but you should really get KMR or Just Born. The powder is more economical - mix with hot water (or it won’t dissolve); make sure it’s not too hot when you feed her, though. You need to feed her every 3-4 hours right now. She should be taking in 8cc of formula per day for every ounce of body weight (so if she’s 10 ounces she should be taking in 80 ounces per day, divided by 6-8 feedings), and should be gaining 1/2 to 1 ounce every 2-3 days. Use a kitten bottle - you can get them at PetSmart - it’s called a Pet Ag bottle, and make sure to cut the nipple opening big enough (but not too big, or she can drown in formula).
VERY IMPORTANT: if she is sickly or lethargic, and especially if she is cold, DO NOT try under any circumstances to feed her. You will kill her. Kittens of that age cannot digest properly if their body temp is low and they will go into shock and die within a few minutes. If you think she is crashing, slowly give her a 5% solution of Karo corn syrup and warm water through a syringe (without a needle). Don’t give her so much that she chokes. See if she perks up and if so, you need to bring her to a vet for subcutaneous fluids and possibly other medical care.
Once she gets to be 4.5 weeks old, you can start weaning. If she’s healthy, you will probably be able to tell she’s ready because she’ll start biting the nipple. You can start mixing the formula with a nice smooth kitten food (not adult food - and the smoother the better - Iams is the smoothest but some kits don’t like it, so you might want to put some other brand through a blender). Make an thin oatmeal-like porridge and try to get her to eat it off your finger, then from a spoon, and finally, hopefully, from the bowl. Warm it up in the microwave but make sure it’s not hot. It takes a lot of time - don’t try to force her too much. If after several days of trying she still won’t eat except from the bottle, she is probably sick and needs to see a vet. As time goes by, you can decrease the amount of formula (replace with plain water) until you have just water and wet food. Once she eats wet food easily, you can start adding some dry crunchies but it’s a good idea to break them up with a hammer at first, because they are usually too big for tiny-kitten teeth.
The most important thing these kittens need is to be kept warm and to NOT be fed if they are cold. Can you set up a heating pad, on low only, with two layers of towels on top? They need outside-generated heat; they cannot regulate their temp at this age and need another heat source. This is why kittens huddle together and with the momcat.
Read the Caring for Orphan Kittens manual at kittenrescue.org. It is extremely informative. If you have any other questions, send me an email at my profile address.