I raise hand fed lovies and I wait and pull them from the nest closer to three weeks of age and have had no problem with them accepting a syringe, especially at the second feeding! They are fed every 5-6 hours throughout the day, with last feeding being at MY bedtime. Then they get breakfast first thing upon my rising. My feeding routine might be 8AM, 1PM, 6PM, 11PM. I believe if you pull them younger you should feed at least once overnight.
You should, by all means, learn to hand feed from an experienced breeder. The syringe must be placed correctly, formula has to be about 102-104 degrees. You need to know about sour crop and other potential feeding problems. I recommend you purchase and read "Hand-Feeding and Raising Baby Birds" by Matthew M. Vriends, Ph.D. It's a wonderful reference.
