Before we moved in I think there was an old porch on the back door which they took down. We're now left with what I can only assume is old, dry and very hard silicone or something plus paint on the bricks. As you can see I've tried to get rid of some of it with a wire brush attachment thing on my drill but it just seems to be making a mess of it. Any advice on how to get rid of it because there's some on the front door too and don't want to make a mess. Thanks