In the Northeast, we have no need to detune tips and tails, since a few descents on our typical "snow" during in-bounds resort skimo training will take of that.
However, we aren't immune from the laws of metallurgy, or whatever science dictates how steel edges will rust if melting snow isn't immediately removed on the drive home.
A gummy stone -- or gumi if you want to be more Euro about it -- is perfect for removing rust. It's essentially a super-abrasive version of a rubber eraser. So just enough abrasion to remove rust from your base edges without removing any noticeable that would over-bevel your base edge (since we desperately need as much sharpened steel as possible on our skis in the Northeast for that aforementioned "snow").
Overall, an absolute must-have for your tuning kit.
Comment on this review: