Having never had the problem with stains, I don't know the best answer to how fast to bring up the chlorine, but I would just say to do it gradually while keeping an eye on the pool and stopping if you see stains beginning to form.

As for the metal magic, it doesn't change the metals into salts, it just keeps them sequestered in the water so they don't deposit on your pool. Flocculants are usually used to gather small particles that are floating around in your water and make them stick together to make it easier to vacuum them out....but they are not going to change your metals situation. Unfortunately the only reliable way to remove the metals from your water is to replace your water.

Janet