Looking ahead to next pool season, she wants me to clean the scale from the tile in our inground pool/spa. I tried acid and a scrub brush last summer, and it didn't dent it. I'd like to clean this myself rather than hire a pro, but I don't have a compressor or anything like that to power it off. I see a line-away drill option available online - it's a round pumice stone fit onto a drill mandrel - for ONLY cordless drills of course. Is this the answer for typical glazed tile in a pool?