I never mask with the 5200, I just find that it cleans up well enough that it is more efficient not to worry about it, slather it on and wipe it off. Sometimes I do see some staining on really flat paint, but I'd prefer 5200 then paint.
I don't think you will do all that well searching...
I bet that makes a mess. If I'm working on a serious project, I often keep the rag in a plastic bag to use it multiple times, but for sure that is a one way path for a rag towards the trash.
Far too often I see pictures here of sloppily applied marine sealant and even worse white marine sealant being used on a duckboat. If your boat looks like a bagel that is on you (or whomever you paid too much to apply the sealer) because it is so easy to fix with a rag and some appropriate...