Straight detergent. The original recipe says use dawn and heat up the vinegar. But I had an old bottle of Johnson and johnson no tears (I hate the stuff!) and used that, and vinegar straight in an old spray bottle. I rinsed it and thought uhoh didn't work but then I out my finger on the scum and it moved just with the tip of my finger. Amazing! I think it would work really well if done once a week you might find you get no build up and don't even have to wipe will keep you updated.