With my first two rats, Wednesday and Pocus, I would just hold their faces, stick the syringe in their mouth, and would usually be able to get it all in their mouth before they put up much of a fight. Our third rat was a completely different story. She didn't like to be held much, and wasn't a big fan of us humans. I tried to hold her a lot and get her used to being out of the cage and hang out with us like the other rats do but she wanted no part in it. When she got sick the first time and needed meds it took 20 minutes of chasing her around to get her to cooperate. So, I took the tip of the syringe after I got the dose in there and smothered it in peanut butter. She came right for it, and it was thick and sticky enough that by the time she had licked it all off I'd given her all the medicine. The other rats smelled it and started trying to fight over it, haha. I only had to use that trick a few times, and then any time they saw it they would fight over who was going to get it. Now, they grab it and hold it with their hands right away, with or without the peanut butter.