I had 2 different ways of 'training' my boys.
Same as you, afraid that they may not have enough nutrients, during lunch and dinner, I'll feed. But during snack time, I will prepare things like coco crunch, maybe just 5 pieces for practice purposes, with a table-spoon (the one we use for drinking soup), cos the sides are higher, hence the food will not fall off so easily.
Is introduce at playtime!
Find a bucket full of crushed small paperballs.
Ask him to use the tablespoon to scoop from one bucket to another....
What you are training is the hand power and hand control...
soon the kid will be 'addicted' to being independent, cos' they feel proud of themselves.
And naturally, when you can tell that the hand control is good enough, you can do it for actual mealtime.
As you can see, my 2nd method will give them a sense of achievement. But during mealtime, they will find their own reward. their reward will be to be able to munch the food they love and satisfy their hunger.