I used to clean snails with a pocket knife and wire brush....The pretty snail in the pic isn't too bad about becoming encrusted, although some are. More importantly, they are usually associated with kelp, and are cold-water species from the eastern Pacific. You could probably get some fairly easily, but you'd need to run a refrigerated tank, and I'm not sure how easy it would be to grow the algae they need to survive (although I know it's been done). It would be a lot of trouble, but would make a fantastic species tank.
Cheers,
Don