I've used full strength star sans before on scratches. Why full strength? Mainly to keep it in gel form so that it will stay on the vertical surface. Just a small dab on a rubber spatula and smeared over the scratches. It won't drip off. I usually leave it on for several hours and...
I rinse in hot water (ie. mash temps). They smell terrible. I don't care what anybody says - the smell will be in your mash if you don't use hot water soak then cold water rinse