When my boil ends and I've pitched yeast I use the hop bag and leftover chilling water to scrub the inside of my kettle. It takes the foam ring you're describing off without removing the oxidation of aluminum.
During the boil, and I think this was more your question, I do as Dsorenson does and try to knock it back. I've found I only get good, lasting foam at hot break. If I add hops during that time they all stick to the edge (I use pellets) and don't spend much time in the wort. After letting the hot break fall back into the boil I'll do my 60 minute addition and start the boil timer. It probably doesn't matter much what you do with it, though someone probably has some data about the hot break being good for head retention or yeast nutrient or something. I dunno, just speculating. Kyle