I used a hair dryer, then used a safety razor blade parallel to the bottom edge to push straight down (from the glass side, towards the back) while lifting with the suction cup. I wiggled the blade (top to bottom) while pressing down gently, until I saw a gap that would accept the spudger. It did not take much force on the blade or much wiggling, just patience.

"Moderate difficulty"?? There's only three steps and two of them involve removing and reinstalling the battery door.