Hi Liza! Agree with the earthworms, they will find their way easily..the only thing with composting directly on the ground, find a spot away from your house a bit..because, it will attract ants. Though the ants will also help in the composting chore.
And I totally agree with you about eggshells..I also grew up in the Phil and I do remember seeing orchid shells, almost still whole but emptied out, right at the tips of some orchids.
I do composting too, but I use a double tumbling bin. I read somewhere coffee grounds are good for the garden, especially when battling the yucky snails/slugs.