Do you have two people available? DH and I had the best luck in holding Chilli like a baby, slightly on his back. He even reached up to steady the syringe. What kind of antibiotics are you giving?
By myself the way that has worked best for me since I just cannot get the darn squirmy thing wrapped on a towel is to put a pillow on the desk next to their cage, put him in the crook of my left elbow, hold the top of his head, around his ears and syringe with the right hand. This is how I have been getting the CC in him. Also, we found that after a few days, Chilli calmed down and was happy to get his meds.
Another trick I read about was to dilute them slightly with a weak chamomile tea brew. So if he gets .4 ml of antibiotic, I would fill the syringe to .6 total, drawing the tea after the antibiotics.