My hardcase for my banjo had several white scuff marks on it that I wanted to remove. Many musical hard cases, like the one I have, have an outer covering of vinyl. Most paint removers will eat into vinyl and many gentler cleaning solutions aren’t strong enough to remove scuff marks. I heard that Mr. Clean Magic Erasers work well on vinyl floors so I decided to try them on the case.
I had never used a Magic Eraser before but they are very easy to use. You simply wet them in water and use them like you would any scrub sponge. They do fall apart as you use them. I was able to remove all the scuff marks from my case with 1 Magic Eraser but the eraser was pretty much used up by then. These things should work on other hard cases as well. I tried in on a violin case that had much less texture than my banjo case, and the Magic Eraser worked on it too.
In the end, I would definitely recommend Mr. Clean Magic Erasers for removing scuff marks from musical instrument cases. They are easy to use, won’t harm vinyl, and they work.
Here is a short video of me removing the 2 scuff marks shown above: