My daughter just had her second scope today.
Prep is easy. 2 Dulocolax tablets at 12 noon. Then starting at 3 pm, empty and entire 238 mg bottle of Miralax into an entire 64 oz. bottle of gatorade (no red or purple obviously). Drink that gatorade mixture over the next three hours, with the goal being to drink 8 oz every 15 minutes. If not cleaned out, take more Dulcolax. That's it. Very simple.
My daughter can't tolerate even the Gatorade so we used apple juice instead. She also can't drink that much liquid in such a short period of time, so we started her earlier in the day (about 12 noon with the juice), and the cleanout last longer (till about 6 pm till she was emptied out.) She did fine and was cleaned out after only about 4-5 trips to the bathroom. She's tiny so it was fast, but this same prep method was used by my husband when he had his scope last summer.
Hope this helps.