peeling off the outer casing completely wont work as well, many factors go into seed germination of fruit trees, and shrubs, the seeds must be ripe, just like cannabis you wouldn't try to germinate that immature greenish seed. like mentioned many fruit species require a cold period, many commercial nurseries have large refrigerated rooms for this purpose. This is also part of the reason commercial growers clone and reproduce their plants asexually, especially if you are trying to propagate a specific trait quickly in a plant. Usually seeds you buy from a seed bank are ready to plant, and tests are done to insure germination rates are constant. Also keep in mind if you are trying to get the same juicy apple that you ate the chances are not necessarily in your favor that a seed in that apple will produce the same great tasting apple. it may or it may not. Though I would encourage planting seeds of shrubs and fruit trees because it will promote genetic diversity in a species, instead of buying a cloned plant at a garden center. to me the quickest is stratification, obviously you dont want to peel off the whole case, but little incisions with a knife, or rubbing one side with sand paper as mentioned. or letting them sit in a acidic solution overnight. Keep at it though I'm sure it will work out.