All and all, some solid advise but we are over-looking an important fact-there is some problem with the tank that has allowed the animals to get sick in the first place! Ick for fish isn't much different then the flu bug for us humans, we are always exposed to it but if we are heathy our immune systems can deal with the infection. I would suggest some careful water testing to determine what the under-lying cause is and then correct this. NO treatment will work if the causes of the infection aren't corrected first.
Sharks don't usually get ick infections but if their environment isn't up to par then they can and will suffer heath issues. There really isn't any medications that can be safely used with elasmos. Formalin baths can be done but are very risky. Never, ever treat a shark with hypo-salinity. Sharks that are already stressed will not tolerate the drop in salinity and will only make matters worse. Copper shouldn't be used on any shark. With regards to Scott Michael's suggestion that nurse, wobbies, etc can be treated with copper, I have found from professional experience that these sharks after repeated exposure have difficulity locating prey and navigational issues in their tanks. The copper ion is a very large metal ion and will easily block the shark's ampullae of Lorinzini (their elctro-receptors) and the lateral line. Sharks kept in the proper conditions to begin with and fed properly will simply not need to be treated because they won't get infections.