The Kelley protocal says, "Preparation: Drink as much Organic (or 100% pure) APPLE JUICE as comfortable, for 5 - 6 days before the liver flush, in order to soften gall stones."
I imagine it's the same with apples - just eat as many as you can comfortably get down 5-6 days before.
My second flush was great. I ate about 10 apples and drank 1 gallon of fresh apple cider starting 3 days before the flush. I've heard people say green apples (Granny Smith) contain more pectins, but I bet they all work. I mixed up Fuji, Granny Smith and Braeburns. My stones were much softer this time. While I don't know if this was the apples or just deeper stones working their way out, I'm going to keep eating apples before flushing.
Health food stores also sell Apple Pectin in vitamin form. I may try adding that to my regimine next times as well.