This is also done on an old kitchen cupboard door. It originally was left like this and I used a toothpick to scratch away at the surface to get the desired effect. I was experimenting with texture and layering.

For awhile I did nothing to this painting. Then one day I decided to give it a makeover because it had always seemed unfinished to me. this is what it turned into.

This is a close-up of the scratchy texture and layering.

i went a bit crazy with this one and I never quite finished it, but it is still a work in progress.