Depending on the size of your larvae, adult brine shrimp are too large for them to eat. Freeze dried versions are more trouble than they are worth, since they must be rehydrated and tend to float on the surface. Better to use frozen brine shrimp that have been minced with a razor blade.
Truthfully though Cynops species larvae tend to ignore non moving food items (though I had moderate success with decapsulated cysts). Unlike many Ambystomid larvae, Cynops larvae live by the rule "If it moves, and is small, it is food"
Better to put forth the effort in hatching out live brine shrimp napuli or, even easier, getting live daphnia and moina to feed them. They will also eat whiteworms and microworms depending on their size.