Snails suck. If this worked that would be awesome and at the same time hilarious. Salt kills slugs, how about snails? Or would that kill the moss too. I am amused at your question. Next will be what happens if you spray the frogs with beer.
Note: That is just a joke. HaHa, well, I guess not that funny. But I am keeping it here anyway.
I have used salt dips on freshwater plants before with pretty good success. What I used to do was get some water and mix in as much sea salt as I could before it wouldn't dissolve anymore and let them sit in it for a few minutes, you will see whatever was living in the plants laying on the bottom when you take it out usually. Then rinse them VERY well with fresh water to get off all the salt. I have done this with Java Moss, Java ferns, and anubias in the past.
The only reason why beer works is that it attracts the snails with the smell, they drink, get drunk and drown. Its more of a trap than a 'cure all', what youll need to do is set up some kinda pipette dish, with a lid to protect your frogs, but enough pace for snails to get in. They will go in, drink and drown. Just make sure your frogs dont suffer the same fate.