Iodaphor works fine. To get an idea of what to expect prior to and after conversion, put a thin coating of water on a white plate and drop a bit of iodine on it. It just stays orange but very dilute just like you'd see when you have full conversion. Now mix a bit of corn starch into water, put it on a plate and drop the iodine on. You'll see purple instead of orange which is what you'll get if you haven't converted.