These brushes are for gentle use only. There is no way to remove sweat slag. I used them to remove rust from some gun magazines I foolishly left in a wicker basket. Tip: Do not leave spare parts for weapons in the wicker basket. They did an excellent job of removing surface rust without leaving any scratches. We are talking about fine rust film, not rust film. You'll need stiffer brushes if you want to remove scale or paint. But if you're trying to clean a delicate surface without causing further damage, they'll likely work. Treat them like toothbrushes and they will work better. Like a toothbrush, the ends of the bristles do the work. If you apply too much pressure, the bristles will flatten out and stop doing their job. And when the wire bristles are flattened, they don't rebound, rendering the brush useless. So brush hard enough to bend the bristles a bit and they will work better and last a lot longer.