While fishy's rule of thumb is a 100% effective rule, I still think it is possible
to use some harsh chemicels in a completely dry tank, that you can then bleach, and rinse, multiple times, and then rinse more, and then let sit out in the sun for a day or two, and make it safe.
it's easier to just not use anythign harsh at all if you don't have to.
That being said, I'm hesistant to spend $60 on a removal kit that is safe for fish but probably not effective. I've got an arylic tank with some REALLY nasty scratches in it. Perhaps once my planted hits it's stride I'll work on getting them out somehow.