The "raining down" technique in blackjack refers to a strategy where a player places bets in a manner that capitalizes on favorable sequences, often increasing their wager after winning hands to maximize profits. This approach aims to take advantage of a streak when the cards are favoring the player and can create a sense of momentum, it also emphasizes the importance of managing risks, as it involves a careful balance between increasing bets during winning moments and knowing when to stop or minimize losses.