Test your water frequently and add the appropriate amount of bleach to get back up to 15ppm. Do this as often as possible, as often as every hour if you can, but at least once a day. Make sure you test and add bleach before bed, and test again in the morning before the sun hits your pool. Initially, the FC will be used up very quickly. The more often you can test and boost your FC to 15, the faster the conversion will go. Toward the middle of the conversion, it is more prudent to test and add your bleach in the evening, or at other times when the sunlight is not directly shining on your water.