THings that worked for us: location, location, location. DS would eat at the kiddie picnic table, and later at his little wood table, but not at the big table. Also maybe try booster seat vs. car seat. Have a picnic. Let him eat a bite, then get down, come back and get another. We pretend that dd is a "lion" and give her bites between the slats of the chair (yes, great table manners). I also love to feed my dd in the swing outside. She will eat a huge bowl of rice and veggies, or macaroni, or anything. She gets a bite, has to finish it. I push her. She is done swinging, she gets another bite. Oh, and no clean up LOL
Get different plates, different utensils. Feed him. Let him feed himself. Let him feed you. Line up cars, little people, feed each in turn and then a bite for him. One for fireman, one for Sonya Lee, one for Michael, one for ds. Ummmm, Dr. Sears has the "ice cube tray" trick leaving out snacks. I snack my kids all day long. They also get two breakfasts, one at 7 am and one at 10.