What is the most effective and safe home or over-the-counter treatment for keratosis pilaris on upper arms and thighs?

Options: Often, over the counter exfolliants are used like creams containing alpha-hydoxy acids, lactic acid, salicylic acid, or urea. Everyone's body responds differently to the various exfolliants so there isn't one that is clearly superior. Sometimes mechanical exfolliants are used too, like in creams/lotions with crushed walnut shells. Even nonprescription retinol based creams can be used.