I had the same problem with pilling one of my cats (who didn't?) and I was jealous of the vet who did it so easily. I asked him to show me how to do it. If you grab the skin back of their neck (where their mother carries them) and pull back a little, they will freeze, and won't move at all until you let go. With your other hand you can easily open their mouth and put the pill where it should go. They will swallow it. The trick is to find the right spot to grab, but I'm sure if you ask your vet he will show you.
There is another way with holding the cat's head, but than somebody has to hold down the rest because you risk scratching otherwise.

This demonstrates both, but with the second it could scratch it it wanted to.

watch?v=GQ330ikMi8M

(don't mind me, just one of your long time lurker is trying to give you advice :) Sorry if it's double, but the first time it said the comment was marked spam (probably because of the youtube link I cut in half now)