I recently discovered that a toy I already had in possession is working GREAT for slowing down my dog-food-gulper.
JW Pet Sphericon Football Toy
A rubbery-football with many holes in it. Or a rubbery-ball with many holes in it works as well. Personally I felt the holes were TOO big for a treat dispenser so I just had it laying around. Then one day I put it in the food dish, poured the food on it, pressing the kibble down onto it. It works! He does not take out the football and shake the food out, he eats and nudges it, leaving it in the dish. Results may vary with your dog, ha!