The first trick is rotating between "High" and "Low" stacks each day, effectively cutting the cards in half yet still covering every operation each day.
The student merely starts with a single thirty card set, with one card, and slowly adds cards each week until all thirty are mastered. "High" and "Low" stacks are rotated each day. Once a set is fully mastered, he moves to the second set, and so on, until all six sets are memorized. However, even fully mastered sets are reviewed each day.
Once a set is mastered, reviewing should take less than a minute (two seconds per card), and to do all 180 cards mastered cards, or a complete stack, will take less than ten minutes. Mastery arrives quickly, because while the student performs every operation every day, only half the cards are needed because the student rotates between the "High" and "Low" stacks. This cuts the invested time nearly in half for the same level of mastery a typical student will experience, and because it is organized by set, it will feel much easier to the student. The light will be clearly visible at the end of the tunnel.
It's fast, organized, and painless. If the student doesn't know a card, he shouldn't strain himself, merely place the card at the back for redo. Remember, the student will soon see every operation every day, and won't be able to forget them!
Now for retention. Once the cards are fully memorized (all six sets, High and Low stacks), there is no reason to repeat every card every day anymore. So the student moves to a six-day (weekly) cycle of all the Highs one week, and the Lows the next, covering only one color each day. Thus, the student sees every operation every week, and yet only does thirty cards every day - a mere minute per day! Guaranteed retention for a minute a day is well worth it. The student continues this until he goes to college, at which point having instant recall over your math facts is a huge advantage.
How does it actually work?