The strategy works on any difficulty, but requires at least 4 players. In addition, the 4 players have handicapped themselves: If a normal Hanabi player says "I give Bob a 4 clue. These cards are 4s", all the handicapped player says is "I give Bob a 4 clue"
I believe this strategy is the best possible strategy, and gives the maximum possible score for any deck configuration.
The idea is in a 4 player game, there are 30 possible clues to give, and we can assign each one a number from 0 to 29. There are also only 30 possible cards, and we can also assign each one a number from 0 to 29.
Whenever a player gives a clue, instead of doing it normally, they add the numbers of his teammates rightmost unclued fireworks, take it modulo 30, then give the corresponding clue. Mark each of these fireworks added this way as "clued". Each person can reverse the process to find out the exact identity of each of their fireworks.
From this algorithm, you can make a strategy that wins the game, because its as if every card was drawn face up.
If there is any problem with this strategy, please tell me. If not, one way to stop it is require that each clue hits at least 1 card.