A.C.
From what I've witnessed, my daughter is just beginning to talk about the potty, the less you force the better. If they are fighting it tooth and nail, it won't be a good experience for either of you. If he seems scared, try to figure out why. I've heard that some are scared of being flushed. It will eventually click, so don't worry too much.
As for incentives...I've heard of using fruit loops in the bowl for them to aim at. One M&M everytime they use the potty successfully. Stickers on a card working up to a bigger "prize". Marbles in a jar for a bigger prize.
Just like with everything else, do what works best for you and yours.