I like the idea of raising humidity for a while. Toothpicks are good too, but the reason I like the water spray method is if you set it to spray a single jet, you can aim it exactly at the place that looks best to lever the shell off without damaging the cotyledons, and you can spray gently at first, gradually increasing pressure until you get a feel for whether it's going to come off or not. The idea came from trying to simulate how nature would do it, with heavy rain... except when they're in nice little pots you can hold the plant on it's side and kind of spray them so the "rain" comes from underneath.