If you have the time to devote, this process will go faster than if you just drop chlorine in and check it the next day. In one post, there's advice to add sufficient chlorine to shock, then test it in just one-half hour... then add more to reach the same level, and do this as often as possible especially in the first day or two. Elsewhere I think it was duraleigh who suggested that you should prepare yourself with 4 times the amount of liquid chlorine needed to bring FC up from 0 to shock level (16 ppm, in your case.) That's a lot of chlorine, but because of the suspect ammonia, you may end buying much more. If it's cheaper in your area to purchase 10 or 12% liquid chlorine, you might want to consider this. Otherwise, go with the big jugs you've been getting so far. Bottom line, I think, is don't give up... add chlorine aggressively (meaning often) and do everything possible to keep the FC at shock level at all times.