I've heard that clavamox has a sweet taste that cats hate. I had to give it to Cindy once, and while I didn't have any problems giving it to her, it caused her to have diarrhea and stomach upsets (not eating). The vet switched her medicine to a pill (not clavamox, a different antibiotic), and I was able to crush it up and mix it in her food.
I also completely understand the problems you're having getting Buddy to take the medicine. Swanie is the same, and I haven't successfully found a way to give him med except to mix it in food, and that doesn't always work. All of the methods recommended are good ones .. if you can get your cat to cooperate
The vet demonstrated for me to walk up to your cat from behind, throw a towel on him, and then drop to your knees with him between your knees. She demonstarted on a very docile cat who did nothing more than say "Meow!" Swanie is off and running before the towel gets near him. If I do get the towel over him, he's gone before I can get to my knees (I'm not as young and spry as the vet). He twists, squirms, hisses, bites if he has to. They sure don't make it easy, do they
Good luck with Buddy!