Let's talk about the reasons why and when you would use the different scrying style cards: {brainstorm}, {preordain}, {ponder}, {serum visions}, etc.
{Brainstorm} is an instant and is best used during an opponent's turn. It's also best to use with shuffling effects like fetch lands so you can put the 2 cards you don't need now back on top of your library and then shuffle them away.