I've adopted the "slug life" and have been nightly applying Vaseline on my face for a week. It has helped with my red marks and reducing inflammation. It has also made my skin significantly softer. It hasn't done anything for my darker spots.
It didn't make my acne any worse, but it did nothing to help my scars. I would cut a fresh potato into thin slices and rub them all over my face then leave them on overnight; I did this for two weeks, no difference.