Besides the spoon trick, sometimes putting a little bite of the food in front of them on the floor, without using a bowl, works. Simon gets intimidated by a bowl full of food when he does not feel that hungry, but will sometimes eat one bite at a time if put in front of him on the floor or offered on my finger.
Re: the sour cream I suggested earlier, he licks that off my finger or eats it out of the container, but will not eat it on the lid or, i think, in a bowl. So it's true that you need to experiment with the manner of feeding as well. Michelle