With the Liquid in a squirt bottle, I sprayed it rather heavily on the stain/buildup and let it sit for about 15 minutes. After which I hit it with a light mist again to re-moisten any dried liquid and scrubbed with a floor brush. When I thought I had removed the rust, I wiped the wet Rusteco from the carpet with a dry, clean shop towel and rinsed it with a clean, wet shop towel before a final dry provided the results you see in the photo. I was very pleased and impressed. Click image to enlarge.