I hope he’s doing better now. That he fought his meds is actually a good sign, even if it’s inconvenient for you.
It is a bit tricky to syringe-feed a bunny, and if you can be two or even three people, it’s much easier. One person holds the bun in his/her lap, sitting up (never put a bun on its back for for feeding), one peron stabilizes the head and inserts the syringe in the gap between the front teeth and the inner teeth. Then push the plunger slowly, giving the bun a chance to swallow each little “mouthful”. The person holding the bun or a third person can cover the bun’s eyes with his/her hand, because that calms a bunny down.
If you can’t get anyone to help you, you need to put the bun in a towel burrito so it can’t box and scratch you.
You can mix Critical Care with sth yummy, like plain canned pumpkin (not pie-filling) or baby fruit or berry purée or mashed banana. Many buns will find this yummy enough to eat from a plate or a spoon, but a bun who is too out of it will need to be syringe-fed.
The only thing that makes you better at syringe-feeding a bun is practice. I of course hope you won’t have to do a lot of practizing.